Have you tried lr-mame2000 ? Should be less demanding than Mame2003.

@levelkro
Hi, I am having same issue. I was unable to get LCD from gamepi20 running at all, not even with different distro.
If you got anything out from waveshare, would you mind to share it across?
Thanks.

Unless it doubles as a handwarmer, you don't got a Pi4 in there...

Maybe a late reply, but if HDMI and buttons works on your gamepi, go back into the terminal and enable SPI using sudo raspi-config. That worked for me.

@jpe230 Can you assist me in this case.. I am really hopeless about the screen issue..