Were there any 8-bit era computers that had a 3.5" floppy? They probably would have run CP/M. I do have an apple IIC+, but I also would like some sort of Z80 machine.
What about the C64? It had both 5.25 (model 1541) and 3.5" (model 1581) drives.
It could be used with Commodore 128, which could run CP/M.
Does Famicom Disk System count?
Some higher-end MSX machines had 3.5" drives as an option.
Commodore released the 1581 floppy drive in 1987, which was for their 8-bit systems. The Apple iiGS had one as well (though it would also work on Macs of the time, as well as the other Apple ii computers as long as they had a floppy drive port (sometimes this meant needing a controller card)).