Solved Profile information does not save

So I guess this issue is dead

Have you updated Kunena in the meantime?
Go to the Joomla Global Configuration (tab System) and set Debug System to Yes. And on tab Server set Error Reporting to Maximum.
In the Kunena configuration (tab General) enable the Debug Mode.
Then try to edit an user profile in the front- as well in the backend. Maybe there is a more accurate error message.

I just wanted to confirm that this also affects me. It is a fresh installation of Kunena 6.0.1.1 on a Joomla 4.1.5 site that was set up directly before through automated scripts of the web hoster (Strato). Unterlying PHP version is 8.0, SSL was activated already before.

Something I noticed is, that this problem seems to affect only "normal" registered users. My "Administrator" account is not affected. It can save profile changes and set an avatar as expected. Normal users also get a positive confirmation after saving the profile changes but nothing is actually stored on the DB.

EDIT:
After carrying out the user synchronization tool in the Kunena Tools section, the additonal profiles were created and can be changed afterwards by the users.

This was actually just fixed for me after I installed the newest Kunena update. That was not an option previously.