I gave their github issues a look and I did not find anything similar to this…

The repo is the correct one. I have no useful advice unfortunately. Either reinstall, use signal or wait for someone who can be more useful.

Is your pixel up to date? Could you please provide the fdroid repo you have added to your fdroid client?

Try enabling “exploit protection comparability mode” on the system app settings.

I do not think this is it though.

If you do not set a passphrase, does it work as expected?

Not available on fdroid yet.