I've actually asked about alternatives in the EndeavourOS forum and talked about it there:
I just found out about DeaDBeeF. Unfortunately, it's not what I'll be using.
It is quite a one-to-one match to foobar2000! It has the same modularity and customization. However, the plugin ecosystem is nowhere as big. There's no Coverflow plugin.
And there was a lyrics plugin, forked after an earlier plugin stopped development. However, the developer quit after decreasing passion coincided with the DeadBeeF developer removing the already finished Russian translation in the wake of the Russian war for whatever reason. Needless to say, I am not comfortable with it both feature-wise and ethics-wise.
Strawberry and all Clementine (or should I say, Amarok?)-likes don't strike my fancies. They seem to be in pretty good hands, but I just don't like the side-tab layout (plus the aforementioned problem with lyrics). Amarok seems to have switched their design, and since I plan on using KDE either way, if the usage is good enough and I can't find anything better, I'll either use Amarok or Sayonara, which also seems promising.