This worked for me for the "This account already exists on your device" issue:
After 2 days of trial and error, I was finally able to restore my chat history. Here's what I did:

  1. Install WhatsApp using Google Play Store but don't start the setup.
  2. Navigate to Settings > Passwords and Accounts > Delete the Google account associated with the google drive where your WhatsApp backup is stored.
  3. Grant all permissions to Google Play Services (reverse this after installing WhatsApp).
  4. Complete WhatsApp setup > enter Google account info when prompted
  5. WhatsApp will then prompt you to restore from backup. (enter your encryption key if you encrypted your back up)
  6. Revoke all permissions granted to Google Play Services in step 3.
    All chat history should be restored
    Worked for me... hope it helps someone recover their history
    8 days later
    a month later

    smx73

    I'd like to point out how i got mine to work.

    I tried installing whatsapp by doing a restore from google, after typing in the email it asked to add account again. When i did it said "already in use".

    I gave google play store, google services framework, and google play services permission to contacts via the "apps" app in grapheneos.

    gave whatsapp every single permission possible

    I went into play store, and logged out of all my google accounts.

    went back to whatsapp and entered the google email to restore again, and it worked like a charm.

    go back and disable every permission possible that you don't want on those apps.

    There's no need to grant every single permission. Google Play Services requires the contacts and network permissions, and WhatsApp requires both the contacts permission and the media permission (can simply set up storage scopes instead), as well as of course the network permission.

    a month later

    smx73
    Thank you smx73. I had the same problem. Fortunately it worked.

    a month later

    Same, this is the only method that worked for me. Thank you all. And I wish that all managers at facebook and all developers who programmed this piece of turd of an app burn in hell for eternity.
    To be clear, as of mid 2023 it is no longer possible to restore a backup by moving manually the files if you have Android 10 or higher (as officially stated here), like we always did... Of course not, this is the easiest, most straight-forward, most clutter-free solution, that has worked since computers were invented, but the GENIUS people at whatsapp had to reinvent the wheel with a proprietary solution that is worse that cat shit wrapped in dog shit that does not work and only makes the simplest of things, like restoring a backup, worse than a nightmare. And of course the could backup option is only with the most proprietary, invasive, evil and Orwellian company of them all: Google; the couldn't in a million years have thought to let us upload the backup files on a cloud provider of our choice, as it would have been such a big brain move the universe would have imploded. Thank you, you at facebook are really the most phenomenal programmers humanity has ever seen. I hope you die.

    The only two methods that now work are: whatsapp's dogshit "chat transfer" functionality, which does not require a GDrive backup, and the usual GDrive backup method. Now, before joining the dark side, I of course tried the chat transfer, but since those braindead people at whatsapp don't even know how to properly implement wifi direct or any other method, 2/2 times it gave me errors, after HOURS of saying "chat restore in progress", and the second time it even deleted my local backup... what a fucking joke of a company you are, facebook, and thank you for deleting without my approval gigabytes and YEARS of data. Luckily, as I have an IQ higher than my room temperature expressed as degrees Celsius, unlike those retarded developers at facebook, I did a full backup on some hard drives. And for those of you reading, the easiest method is to use adb (with GNU/Linux, as it is clutter-free), with this command from terminal:
    adb -a pull /path/on/your/smartphone/ /path/on/your/computer/, and it is lightning fast too.

    So the only method currently working, or at least that worked for me, transferring chats from a normal Android phone to one with GOS installed, is to join the dark shitty side and upload all your data to those greedy mf's at G corp, sell your soul and your virginity, and download it again on GOS. You should avoid all the pain and stress and jump directly to this.

    I wanna point out that the procedure is easier than previously explained here, as you don't even need to touch Google Play Store (probably you don't even need it installed, but I installed it anyways), and you can install whatsapp by downloading the apk from their official website (https://www.whatsapp.com/android/); also, you don't need to give every permission to Play Services, as I only gave contacts, photos and videos, network and notifications. This worked perfectly for me, and I only inserted the Google account when whatsapp prompted me, without any problems.

    After this, nuke everything google related from your phone, uninstall any of their services, and if possible nuke the G account itself (it is easier if you create one from scratch just for the whatsapp backup and then you delete it).

    Thank you GrapheneOS developers and community for this amazing OS you created. It is my first time using it, but I am amazed already. You really deserve all the glory in this world. Keep fighting the good fight.
    Cheers

      19 days later
      6 months later

      ToffoliGate
      Hello everyone, I am a new member here. I give my love to everyone and I am asking Why is WhatsApp making it so difficult to restore backups on Android 10 and higher, especially when the manual file transfer method was so straightforward? Should users really have to rely on Google Drive and deal with such issues? I would be very happy if you could let me know, thanks

      9 days later

      sam1 Hi, I'm having a problem restoring my WhatsApp backup. I tried putting the backup file in /WhatsApp/Databases (I had to create the directory, I think WhatsApp has access to it - I set up the WhatsApp dir with storage scopes), and also in /Android/media/com.whatsapp/WhatsApp/Databases, which is where WhatsApp seems to be writing its backups, but either way, WhatsApp isn't noticing the backup and triggering a restore. Any ideas on what I should be doing different? Thanks.

      Try clearing the WhatsApp cache and data. Then, move the backup file to the /WhatsApp/Databases directory again. This might help WhatsApp recognize the backup and trigger a restore. If not, try restarting your device. With this I am giving some great app advice which will never let you face any problem. That is whatsapp plus apk, I am very happy that I am still using this app.

      Name- Skeena
      Mail- oiginalwhatsappplus@gmail.com
      Web- Whatsapp plus

        smx73 It did not work
        Thestinger in the GitHub issue : πŸ™ˆπŸ™‰ everything works well you just have to give the permissions πŸ˜‡...

        5 days later

        lova7 Please note that you are not giving "great app advice", as "Whatsapp plus" is an unofficial whatsapp apk that is probably highly insecure, could contain malware/spyware/trackers etc., is in clear violation of WhatsApp's terms of service and will very probably lead to a ban of your account.

        The only official sources from where you can safely download WA are the official website (https://www.whatsapp.com/android/) and the Google Play store (https://play.google.com/store/apps/details?id=com.whatsapp). Any other source (even Aurora store) is to be considered highly insecure and could lead to a ban of your account. For your own safety, refrain from using unofficial sources.

        Easiest solution, just performed this as i didn't get the "Recover your chats from backup" prompt.

        1) Copy \android\data\media\com.whatsapp\databases\msgstore-xxxxx
        (your latest backup) to a safe location

        2) uninstall Whatsapp.
        3) Place your msgtore backup file manually in the same location, by creating \com.whatsapp\databases manually
        4 Install Whatsapp.

        Now you will get prompted to restore your latest backup if you have allowed whatsapp to scan your device.

        Continuing this thread, and for the sake of clarity, has anyone tried any backup or transfer method on GrapheneOS? For now, the only reportedly working method is the Google Drive backup, but I wanted to know is anyone tried and succeeded with other methods, because with the GDrive route the backup can have a maximum size of 15 GiB, if you do not wanna pay Evil G for extra space.

        • The only other official method is to use the "Transfer chat function". This, however, is obviously not a backup, as it requires you to have a perfectly working phone, because it uses Wi-Fi direct to transfer the data, and it also requires a functioning camera and a functioning touchscreen. So this is useless for recovery. Also, this method never worked for me, probably because the backup was too large.

        • I've seen some reports here on the forum and in general around the web that some users transferred WA's folders manually and successfully recovered the data via this method (in 2024) (see here), here and here). This, however, is in contrast to what WA officially says on its website, as this method should work "only if you’re using Android OS 9 or below".
          The idea should be to manually transfer the entire folder structure with all the media to the new phone from the old one (or from a "backup" of said folders on a disk) and trick the app into thinking that's the same phone as the old one and this is a re-installation process.
          The overall procedure should be something like this:

          1) Install WA on the new phone. Just open it once but do not do absolutely anything. Then close the app, force stop it, clear the cache and storage, and don't allow it to run in background.
          2) from the old phone (or from a manual backup of the folder structure) copy (using ADB pull) the entire com.whatsapp folder onto /storage/emulated/0/Android/media/.
          3) Open WA, choose language, and enter in verification code to activate.
          4) Now immediately turn airplane mode on to block WA from contacting Google's services.
          5) Grant all permission requests that come up, especially contacts and storage access.
          6) Let WA try to access Google Drive. It should say that it cannot connect to GDrive. A prompt should pop up. Skip, and you should be prompted to restore from a local backup.
          7) If it does not restore anything because it "cannot find a backup", just start blank and let it delete all the folders; then force stop the app, copy all your media and databases in the folders, uninstall whatsapp keeping the content, reinstall it and redo the procedure again; now should hopefully find the backup.

        But I do not trust this method, as it seems very prone to error, and Shitapp can always change some little thing and break the entire procedure in the future. Because, of course, the most sane and straight-forward backup procedure of having a local backup that can be manually transferred (like Signal, SimpleX and Threema have) was a concept so big-brain that Zucc's monkeys working at Shitebook could not handle.

        Has anyone successfully tested the "manual" backup in 2024? If so, please report it by updating this thread and helping all GOS users. Thank you.

        As other people in this thread have reported, this is simply not true @GrapheneOS @treequell
        Seems like you never tried πŸ˜