https://www.gamingonlinux.com/2023/12/dusk-hd-sdk-steam-workshop-out-now-linux-steam-deck/
David Szymanski + New Blood Interactive have released DUSK HD as a free DLC for the retro FPS, but you'll need Proton to play it on Linux Desktop and Steam Deck.
Their modding support is still being worked on though as they had to "basically rewrite the entire game and engine from scratch" and so the full DUSK DDK (Dusk Development Kit) built on the new DUSK is "still a few weeks away" but once done "you will be able to play all the custom maps with both Classic or HD visuals, replace weapons, models and more". It even supports Quake and Half Life maps.
Being able to easily run other games maps seems cool, I guess this is on some sort of version of the quake or source engines then?
The original Dusk was written in Unity and just used the same map format as Quake. I would assume those aspects are still true for the rewrite, but I could be mistaken.