From Hackaday:
https://hackaday.com/2022/11/22/minimalist-6502-system-uses-a-cpu-and-not-much-else/
What I found interesting was the serial output without a UART.

Nice! Always enjoy reading about minimal designs.
Bill

I thought that was pretty cool, too. Looking at his code though, I haven't quite figured out how it's receiving serial characters via interrupt.

One trick I've used in the past to save space on solderless breadboards was to place a 'skinny' 32K SRAM underneath a 'wide' 32K EEPROM using a pair of SIL machined pin sockets. The RAM and EEPROM share a common pinout and so I cut the pin off the socket for the EEPROMs /CE pin so that it doesn't engage the breadboard and I soldered a wire onto the shoulder of that pin. Only one set of wires is required to wire up both RAM and EEPROM, plus the extra wire for the EEPROMs /CE pin.

The 6502 40th Anniversary Computer Badge also does serial I/O using the interrupt pin, and it is a low part count system. See:
http://www.sunrise-ev.com/6502.htm