Restoring high-DPI support was really easy. As is the case with most of the LÖVE 11 changes, this made it so I could get rid of most of my DPI management stuff, with two exceptions:

1. I had to change the relative scaling stuff for the main menu's image elements (because now it's overcompensating for the scale, which I suspect is a bug in LÖVE but I'm not sure since it's not happening anywhere else)
2. since Strangers is pixel-precise I had to override its low-resolution canvases to disable the DPI scaling

Oh, and another nice change in LÖVE 11 is that you can finally explicitly release an object before GC gets to it — which means that for adaptive rendering, I can discard the old buffers before allocating the new ones, which makes that run way more smoothly, especially on integrated graphics! So, that will present some nicer rendering quality and performance to everyone.