RetroPie doesn't use the desktop env (which I think you'd need for VNC) and it doesn't have it installed by default if you use the provided image. While some Pi4 users run EmulationStation from the desktop, it's not a supported or tested configuration and you may bump into problems at some point.
I would start by checking the rest of the peripherals (you mentioned having another pi - use that with the exact existing setup) That should let you know if the original board is faulty or not
If the board is randomly shutting down I suspect it will need replacing
Alright, I'll try that later today. Yeah I also figured it needed replacing.
Just thinking of how to prevent a repeat, could a split-second power outage have caused the Pi to die? While I was playing on it weeks ago, there was a quick power outage a week ago during a thunderstorm, not long enough for the PI to lose power or immediately cause this problem, but maybe that could have fried the electronics? Maybe I need to use a UPS or regulator
So I thought I had better post to say that I solved my own problem. I had to get sync from SCART pin 19 on the Pi2SCART's female connector, not pin 20. I did not know about male SCART leads swapping pins 19 and 20. I hope this post might help somebody else out one day.
@beatbox32 Everything looks good, including your mount. Did you remember to re-generate the gamelists from the RetroPie Skyscraper script? Scraping the data simply add it to the Skyscraper cache located at /home/pi/.skyscraper/cache (which is also a symbolic link if you installed Skyscraper from the RetroPie script). But you need to re-genereate the gamelists for it to create the necessary ES gamelist.xml files and artwork files in the /home/pi/.emulationstation/downloaded_media/ platform folders.
Remember to push space for each platform when generating the gamelists to select them.
EDIT: Skyscraper also checks if gamelist.xml is writable before it starts. It won't run unless it is.
Boom! Now it's working. Many thanks for the education on how the cache system works. I think I had a few missteps along the way where I was mounting the media folders as root and not the pi user, running into write issues initially. Once I resolved that, I apparently forgot to re-generate the gamelist.
try mupen64plus-gliden64. it should be the best performance and compatibility in general, but be warned that it's quite normal for n64 to exhibit poor performance on pi4, but several games can perform pretty well.
I tried uncommenting and changing the hdmi_group and hdmi_mode options in the config.txt, but no audio improvement.....just poor video!
from what to what? i suggest a 1080p60 mode in your config.txt (please provide copies of all configs you edit.). any further lowering of resolution you need to do can be done via the runcommand, although personally i leave everything at 1080p.
please also provide /opt/retropie/configs/n64/mupen64plus.cfg