If you don’t want to deal with breadboards, there are lots of cheap (under $50) programmable Z80 computers out there; here are a few I’ve collected: * Timex-Si

If you don’t want to deal with breadboards, there are lots of cheap (under $50) programmable Z80 computers out there; here are a few I’ve collected: * Timex-Sinclair 1000 (American ZX81 with double the RAM — an entire 2KiB!) * TI 81-86 graphing calculators * Verifone Tranz 330 https://www.bigmessowires.com/mozart-tranz-330/ https://www.bigmessowires.com/mozart-tranz-330/ * Cidco MailStation https://jcs.org/2019/05/03/mailstation https://jcs.org/2019/05/03/mailstation Also, for a bit more money, there are lots of new hobbyist computers out there, including the RC2014, Stephen C. Cousins’ “SC___” series, and the MinZ / eZ-Tiny series. You can solder them together and program however you like, oftentimes including booting CP/M off of ROM, MicroSD, Compact Flash, or floppy.