Judge me, I prefer Dolphin to the absolutely joke that Caja is. Now, you may want to curse me because «WeLl, IT's aN OpEN soUrCe ProJeCT, ConTRiBuTe YOuRsElf»-kind of argument and be absolutely right. But I lack the time and energy, so I just use Dolphin instead and complain online about Caja. KDE 5's Dolphin used to work very well on MATE. Then I gave the order: told comrade apt to upgrade my ancient Debian Bookworm to Debian Trixie. Of course, Dolphin is now broken. In order to un-fuck it, I had to research a bit. And since I'm 100% going to forget what I did, we have this present article to remind me on how I fixed it — NO! Documenting? I know, right?
Yeah, I don't know how to fix that one, I guess I'll just have to accept the Windows 7 icons I used to use on Plasma.
You click any file, it opens a file dialog asking what program to use, and lists no program. You have to type the command manually. It seems to be related to broken XDG stuff, according to Reddit, letting kbuilsycoca6 daemon run seems to have solved the problem.