My browser / operating system: Windows 10, Chrome 150.0.0.0, No Flash version detected
topics stay bold even after read

Can replicate:
My browser / operating system: Linux, Chrome 150.0.0.0, No Flash version detected
Using my phone.

My browser / operating system: Windows 7, Firefox 140.0, No Flash version detected
My browser / operating system: macOS 11.3, Chrome 138.0.0.0, No Flash version detected
Yea I noticed this too

Strangely enough the routines for marking topics as read seem to exist in this version of DjangoBB:
https://code.chipmunk.land/scr.chipmunk.land/apiclone/src/commit/11321faed550702234ef5c2c668068e021f13f39/djangobb_forum/views.py#L403-L404
https://code.chipmunk.land/scr.chipmunk.land/apiclone/src/commit/11321faed550702234ef5c2c668068e021f13f39/djangobb_forum/tasks.py#L32-L52
https://code.chipmunk.land/scr.chipmunk.land/apiclone/src/commit/11321faed550702234ef5c2c668068e021f13f39/djangobb_forum/models.py#L230-L248

I'm not sure what causes the issue yet, unfortunately. Funnily enough though, I never realized this wasn't default behavior… but yeah now that the forum has more threads I do find the bug a bit annoying myself.

It appears Heathercat123 fixed this in upstream APIClone.