Temporarily lost phone, what to do about Signal backups?

Question

I've lost access to my phone, with a Signal installation with a lot of old messages I'd rather not lose. I know that most likely I'll get the phone back within 6 months though.

I would also like to be able to access my old group chats and number in the meantime, on my new temporary phone.

I've understood that if i transfer my number and account to my new phone, my lost phone shouldn't lose its messages, it should just "stop all messaging and calling on your old phone" https://support.signal.org/hc/en-us/articles/360007062452-What-do-I-do-if-my-phone-is-lost-or-stolen-

But when I get the lost phone back, will I be able to reactivate that installation and not lose the history? If not, would I at least be able to create a backup from it, to be able to reinstall and recover the backup? The documentation doesn't clarify exactly what a "deactivated" account is able to do.

When going back to my old phone, I'd be fine with losing the short history on my temporary phone.

Answer 1

Careful: There is a difference between linking another phone to your Signal account and transferring your account to a new phone.

Linking another phone:

If you just link another replacement device, you can go back to your original device and re-link it without the data on your old device being lost. The data of the replacement device will not be synced to the original device. This works only if you have NOT uninstalled the app on your original device. According to Exallium (Signal Developer)

Transferring to another phone

Transferring consists of the following steps on Android: On the new phone, install Signal > select Transfer or restore account > enable permissions > select Transfer from Android device > Continue. If you have transferred to a new device you won't be able to access the data upon reclaiming your original phone!

Currently, we only support phones as primary devices, which means only one can be registered (this has to do with key generation and a bunch of other crypto stuff that is beyond my knowledge).

When a device becomes unregistered (because it was offline for a long time, or because the number was registered somewhere else) we don't delete the data. I'm pretty sure I hit this scenario at least weekly via testing. If you do a device transfer, then we do clear data on the old device after the transfer is completed.

Do a backup on original device if version allows

Also note that Signal v 5.44.3 as well as v 6.19.9 allow you to backup, even after the device is no longer registered

Version 6.20.6 does not allow you to backup after unlinking, as the options to make a new backup are greyed out: