Carddav address book setup fails: Incompatible Carddav provider?
I'm trying to set up a carddav address book in Thunderbird. It is hosted at posteo.de, and synchronization with other software (namely davx5 on Android) works with this account and the URL I used. Unfortunately, after entering username, URL (known to be correct from said Android device) and password, TB seems to be able to connect, but then fails with a rather opaque "posteo.de is known to be incompatible with Thunderbird" message (which is shown in white on a yellow background in the dark theme, and thus barely readable, but that's a different problem).
This is TB 91.1.1 on Linux; the error message seems to be the one originating at
is being logged to the console.
Any hints on what the actual root cause is here? Is this an issue with Thunderbird or posteo's DAV server? What details should be included in a proper bug report to the responsible party? Thanks!