uxn emulator
uxn is a small VM for very limited portable retro apps. There's a Linux emulator, but it's annoying to run since you have to install SDL2 on the host, or run it in a container. The windows also use the SDL window decorations, which are not great, and there's no way to set the scaling factor, so on many modern displays apps are tiny.
It'd be great to have a GTK launcher/emulator for uxn apps that just works (TM) as a flatpak, with a list of ROMs and the ability to change certain settings at runtime (similar in structure to e.g. Boxes).