This is absolutely amazing work all around, thank you so much! I am just having a tiny problem though that neither computer I am trying this on is liking the resolutions/fullscreen mode that are picked. It's either blowing up video on my 4K monitor so I only see the upper left quadrant (for the 4K games, and/or not using OpenGL), or it's blowing around all sides, like it's displaying around 125% zoom and cutting off all 4 edges (with OpenGL).
When I look at the Daphne log I see it's forcing fullscreen and specific resolutions, depending on the game. Is there any way to override it from doing this? So I can just manually set fullscreen and/or res for the game? It seems like those are "untouchable" beyond what can be tweaked in the "Advanced" box unless I am missing something (if I set -x/-y it still forces fullscreen, just changes the entire display res instead of a window size). When I use the command lines from the Daphne log but without forcing fullscreen it at least works ok.
Seeing similar glitchiness with fullscreen/res selections on both a PC with a Geforce 970 (yep, old..) in 4K and a Surface Pro 8 with Intel graphics (not full 4K but better than 1080, which might be some of the confusion since it's 3:2 aspect ratio).
Again, this is awesome, and even with the glitchiness I've been spending the last few days deeply stuck in 1983..