

ooo. this is a good question!
not sure about free or CalDAV, but i thought that proton mail was putting in some calendar function, and eteSync also do calendar, however, it is their own protocol (i think), not calDav. check it out though, it may work with an external CalDAV server?
what command line options are you needing for audio? i use kubuntu, and the only reason i hit the CLI is to provide a special output so i can implement multiroom audio, with Snapcast.
Otherwise, i think i could install most stuff without it. OO, maybe spotify needed to add an apt repo, however i think there maybe a seperate installer (snap?) which would negate that.
i feel like you were not going for a vanilla instance if the latest kubuntu/ubuntu needed work.