It’s not like they’re stuck on some outdated proprietary engine like RPG Maker. Minetest is under active development, with a small list of dependencies that are also under active development. It is under no particular rush to get off of X11/Xwayland.
And there’s a separate effort called Mineclonia.
The Steam Deck only does VRR over Displayport. Valve has their own engineers working on every part of the software stack. It’s their own hardware and their dock. With all that, Valve still can’t get VRR over HDMI to work.
Fuck the HDMI forum.
When you can’t fix something, it’s usually “the OEM is doing something insane in their ACPI code”, or “you have a cracked MLCC somewhere, which pushes power delivery barely out of spec and some net doesn’t make timing under complex microarchitectural conditions”.