ZDoom

If you like Vim-style keybindings, Zathura is a good option I had found. Otherwise, I use Evince.

Not Doom-like, but a Quake-style DM game I play, Xonotic.

It's under GPL-3, since it's in the Darkplaces engine (since the game it forked from, Nexuiz Classic, is under GPL-2 or later).

I never knew about this thread, but here's my shot at it. The name's Nëïgsëndöïg Cöcülës (IPA: 'nig-sɛn̩-dɔɪg 'kʰo-kʰju-ʊɫs), a member of the Free Software community, as well as a GNU/Linux user specializing in gaming, privacy and security. In terms of Doom, I'm somewhat new, but have seen videos of ...

This is my first post on here, so bear with me on this front: I'm trying to run a pack of 8 mods recommended by a YouTuber (MutantMods) who focuses on infinite replayability through Doom RPG for Doom 2. The mods are as follows: Doom Roguelike Arsenal, with subsequent monster pack and EXtended ...