Ah yes, it seems I overlooked that when I deactivated all the plugins and only reactivated the persona theme.
Seems to be working to a fashion, just need to get some plugins I rely on updated.
After login i got query for 2factor. I enter the 2factor and then i got 502 error, 'forum is offline'.
That's the link i got for redirection -> https://domain/login/2fa?next=/categories
When i reload site all is ok. Any idea/hint for me?