I wonder when on earth this will be fixed. I rambled about it before and it has been noted as a bug. There's something wrong with the desktop directory.
I use my desktop as desktop, not home folder ( although it doesn't work either nore the folder widget). Since plasma 5.21, certain servicemenus simply don't appear in the context menu and certain custom ones don't work.
For example, the "copy/move" service menu doesn't show on the desktop files (only in dolphin itself). The "show target" entry doesn't show on desktop files either. So, I made a bunch of servicemenus myself in order to have those functions on the damn desktop. The custom made copy/move/link functions work, but the custom "open containing directory" doesn't, nore does the assigned shortcut. In short, unless you don't make some functions yourself to begin with, of which certain won't even work altogether, it's ...messy, to say the least. This kinda core uniqueness stuff like desktop folder widget and desktop functionality became kinda half obsolete for, by now, five plasma versions ( at least). For a full functionality, you simply HAVE to use dolphin. What's the dam point of having a desktop then?! A wallpaper and some working widgets?! In the screenshot you see that custom menu. I made it to have those functionalities on desktop files. The default "open containing folder" doesn't show at all. https://imgur.com/a/oWpsODQ. It doesn't matter what mode you run the desktop either. Desktop, home or custom directory...won't work. Folder widget? Won't work. https://imgur.com/a/YeFbthW Like I said, it ain't just that one service menu, there are a couple that simply don't show or don't work on the desktop, no matter what directory one sets it to.