A new cheat code for the Sega Saturn version of Doom has been discovered, 27 years after the game’s original release in 1997. This newly found cheat allows players to make walls in the game semi-transparent, offering a unique gameplay feature that was previously unknown.
IIRC Doom didn’t have a skybox per se, just parallax ceiling textures. You could put that texture on floors or ceilings and it would show the sky texture that would not be attached to the walls.
The texture was definitely funky and I want to say was used as the ground portal in a lot of Ep3 levels.
But I THINK that was still applied to a giant box on the edges of the map. Which is how a lot of games still do that.
As an old school doom mapper from the 90s, it absolutely isn’t. You build a room, apply F_SKY1 to the ceiling, and that’s it. The engine renders it more like a wall, but it’s not a traditional skybox in that it doesn’t exist in the level geometry outside of the room it’s applied to.
https://doomwiki.org/wiki/Sky