But I suggest RISC-V RV32I or RV32E [1] is a great option too. Only 37 instructions that a compiler would generate from C (etc), mostly simple register-to-register arithmetic and control flow, plus byte/half/word load/store with only one addressing mode.

It's actually, I would say, slightly simpler to learn what the instructions are than 6502 or Z80, and *vastly* easier to use to write useful programs with.

And it's not only for emulator, you can buy a vast range of new hardware today, ranging from 10c microcontrollers (with 2k RAM, 16k flash for the program, 48 MHz) up to a $2500 64 core 2 GHz 128GB RAM workstation, with in the middle ESP32s for a couple of bucks, Raspberry Pi Pico 2 or Milk-V Duo (Linux! In 64MB at 1.0 GHz) for $5, and on to quad core 1.5 or 1.6 GHz Linux SBCs for $20 (VisionFive 2 Lite), $30-$50 (Orange Pi RV or RV2 with 2-8 GB RAM) and so on.

Online tutorial:

https://dramforever.github.io/easyriscv/#my-first-risc-v-ass...

[1] 16 registers instead of 32, as seen in e.g. the $0.10 CH32V003 microcontroller