Some app icons (but not all) in some icon themes are not being detected/used. For example, if I select Faenza icon theme, icons for Terminal, Rhythmbox, Files and some others seem to not be from Faenza theme, but some other:
This is strange because I know for a fact that Faenza does contain icon files for these apps, and also this problem has not existed in the previous versions of Ubuntu (<20.10). The same problem happens with Numix theme.
On the other hand, Numix Circle seems to not suffer from this problem:
I've had a similar, but not identical, question before. The work-around from that topic does not help now.
How can this be fixed?

