Scaling is messed up after Kubuntu Upgrade from 22.04 to 24.04

Hey there,
after the Kubuntu Upgrade from 22.04 to 24.04 the native KDE apps respect the set scaling factor, whereas the rest of the apps (Firefox, Thunderbird, Easystroke, …) are scaled too large.

Has anybody the same problem?

And where could I report this bug?

Best greetings,
Thomas