I'd say the last versions of CP/M for the Z80 - particularly on the Amstrad CPC128, PCW256 and PCW256. We had a whole lab using PCWs as standard equipment, including one sitting at a 3000V DC offset in a perspex cage (controlling part of a C14 accelerator). CP/M 3.0 did bank-switched memory, so the graphics were switched out and you could copy the user-space utilities in to a RAM disk on startup. It was reasonably easy to write RSXs (analogous to TSRs on MS/DOS), which can be handy on a single-tasking OS.
Supercalc2, Maxam2, dBASE II. You could do a lot with CP/M software, especially if you had access to a hard drive which would eliminate the "insert floppy disk X into drive Y" tedium.
V20 is an interesting CPU. A 8086 compatible with support for some instructions of 80186 and 80286, some custom instructions, an 8080 emulation mode… The datasheet describes the instructions using a non-Intel notation that looks very unusual.
I wonder if anyone used CP/M-86 back in the day? I used CP/M 2.2 and 3.x on Z80 pretty extensively. But on 8088/8086 it was MS-DOS everywhere. Were there niche CP/M-86 apps or use cases?
DR-DOS (https://en.wikipedia.org/wiki/DR-DOS) was reasonably popular, and was a derivative of CP/M-86. I never saw the original OS in the wild, though.
I knew some shops that went CP/M-86 because they were big CP/M-80 shops and thought the price difference was worth a presumably lower conversion and training cost. Didn't last long since MS-DOS ate the software world, which is all that mattered.
They used it at my high school in Denmark. It was easy to share hard disks across many machines and the ability to multitask was also very nice. The office people could switch between word processing and calendar software easily, for example.
https://github.com/skx/cpm-dist
I found the compiler collection here useful too:
https://github.com/davidly/cpm_compilers
Though I guess some of these things won't run under the linked emulator, because they use SUBMIT and require more than a single-executable to be run.
(That's the reason why my own emulator used the CCP/"shell" rather than just limiting itself to running FOO.COM)
https://en.wikipedia.org/wiki/NEC_V20