>>11854620
ScummVM has a setting where it will integer scale both axes separately to try to get as close to the proper ratio as possible but with even pixel sizes
For example here you end up with 4:3.125 instead of 4:3, but aside from the ratio not being 100% perfect the scaling is clean
Of course the higher res your display is, the closer you'll be able to get to the proper ratio

AFAIK Retroarch doesn't have a setting or shader that does this automatically but I know you can scale both axes separately manually in the scaling settings to get the same result