What we know
A port of the id Tech 4 / Doom 3 engine to WebAssembly. Its developer says it also runs on phones but is not playable there for lack of touch controls.
Source and tools
Deep dive in progress
This page is a short entry. The full write-up (original game, who built the port, how to play, creators and sources) comes next.
You will need game files from a copy you own. The engine is open source. Not legal advice. Never run a launcher or download from a page you do not trust.