This project was a nice find -- I was able to hook Pi 3B+ (tiny box on top-left) up to my Commodore 1902 (in Composite) mode -- switching to any 8-bit machine in under 6 seconds:
Not pictured was C128 VDC 80-column which comes through very clear but using the middle Composite setting: Separated, not RGB which likely needs a different timing setting.
Started it up in C128 composite mode:
Entered GO 64:
Switch over to VIC 20 composite mode:
Tada!
Now to install a copy of Mega-Cart rom on this SD card.
I have BMC installed on a Pi zero 2 and even on that little thing it runs a pretty decent VIC-20 emulation. It's kind of nice to have a VIC-20 that will fit in my pocket. (Sans keyboard of course)