Porting to G0x1
I reckon the upcoming G0C1/G0B1 ought to be successful. We should add support for their USB cell.
They call it USB full-speed host/device interface, and it appears that they extended the existing dev/fs with backwards compatibility. Host bits seem to be a simple addition in register description, occupying the high halfword. (We should probably ignore the host functionality...?)

G4 map for comparison:

One notable change is the 32-bit PMA access:

Which of our implementation files would be an appropriate starting point?
Cheers
I think it's close to L052. Unfortunately, there is no proper G0 on the local suppliers stock.
Yeah patient we must be
Mouser has a few pieces stocked.

G0s a widely available now, you can get several nucleo G0 kits from mouser.
That's good news!
The PMA on the G0 is 32-bit access only. The rest is more or less the same with some reg names changed.
Created PR #123.