I have on my Fairphone 3+ the newest OS of the Dev-Branch 1.10-s-20230413279105-dev-FP3
I see here that I would probably lose all my data if I switch to the stable-branch.
What would be the easiest way to backup and restore my data?
With TWRP I see, that there is “data (storage excluded)” on Backup. I don’t know why.
When I tried to upgrade with adb sideload the images that are linked didn’t work as described here: https://ota.ecloud.global/api/v1/FP3/dev “Failed to find update binary Meta-In/com/google/android/update-binary” The other links were misleading in the contex oft adb sideload
That’s a TWRP design decision. You might consider to use a tipatched TWRP version. But anyway - I think TWRP is unable to decrypt (and so backup) the internal storage of the “s” version (see e.g. also here).
AFAIK the current FP3 dev and stable versions are to be flashed via fastboot (well, there’s a shell script doing this) and not applied via adb sideload (was different in the past).