TheGodfather
Actually whatsapp does allow you to use local backups, but it is a bit tedious. I have been doing it for the last few weeks and it has been working fine.
The first thing you should do is to backup whatsapp chats in the app settings making sure it is saved locally (as a precautionary measure save it to your drive account). Then you must go, using a computer, to the Android/Media/com.whatsapp folder.
Inside com.whatsapp there will be a folder called WhatsApp. Copy this entire folder and transfer it to your computer (depending on the size it may take more or less).
Once the folder is copied to your pc you delete the whatsapp storage and uninstall the app (I restart the phone also in case any service is still running). Once all this is done you reinstall whatsapp and start configuring it. DO NOT MAKE IT COMPLETE. You must reach the confirmation of the phone number.
After this you reconnect the phone to the computer, go back to the folder Android/Media/com.whatsapp and replace the folder that is inside by the one you have saved on your computer and wait for the transfer to complete (If the folder does not appear do one more step of the configuration until it comes out).
Once done you can finish configuring whatsapp. You will see a screen that will tell you that it has found a local copy and will ask you if you want to restore it.