The list if enabled on ublock origin (firefox android more precisely mull a fork) blocks the loading of https://discuss.kde.org/ which should not be a "malicious" site
Ok after a bit of testing with the custom rom (divestos) and browser settings, it seems that I actually managed to solve it, although I didn't quite understand what the problem was. I'll close for now.
The list if enabled on ublock origin (firefox android more precisely mull a fork) blocks the loading of https://discuss.kde.org/ which should not be a "malicious" site