Are you familiar with restic? if so its very easy to put your phone into a restic backup location too. I use it to copy changed files from phone every night.
First sync is a bit slow but other syncs are very fast if you ignore inodes. (they change at a new sshfs mount)
You could install a simple ssh server on your phone and when you need to backup you just start it and mount it on your computer. where you could have a text file of folders to backup. like
/mnt/sshfs-graphene/Images
/mnt/sshfs-graphene/imporant
/mnt/sshfs-graphene/backups/sms-inport-export
/mnt/sshfs-graphene/Documents...
Etc etc. then run a command like
restic --password-file=.restic-passwords/phone-backups /mnt/path/to/resticbackup backup --files-from /mnt/path/to/backup/file-location-input-file -tag 'Pixel7-GrapheneOS' --ignore-inode
after mounting the phone with something like
sshfs -o follow_symlinks,reconnect,ServerAliveInterval=5,ServerAliveCountMax=3,compression=no -o ro user@ip:port /mnt/sshfs-graphene/
That lets you mix and match whatever folders you want. and you get it off the phone in the same go. its fast over local wifi first sync takes a hour or 2 if you have alot on phone but after that im sitting on like sub 5 minute syncs. often done in 1-2 mins
Never had a problem with it for the years ive run it. downside is the computer you mount phone on will see the data on phone. so might not be for everyone.