Why the theme change?

The theme that I had configured for the forum seems to have disappeared, and I now see the default opensuse theme (or is it called a "style").

I don't mind the opensuse theme itself. But I am now back in the situation that "mark forums read" does not work. That's why I changed themes in the first place.

Can you either fix the opensuse theme so that "mark forums read" works, or else restore the alternative theme that seems to have disappeared (or both).