What games have you played with community run multiplayer mods? - Divisions by zero

For example Project Cartographer describes itself as the following > Project Cartographer is a modification for Halo 2 PC (Halo 2 for Windows Vista) that restores online play (Microsoft abandoned the LIVE servers) and adds additional features that are not present in the base game. Before the release of Master Chief Collection it was my go-to for playing online. Similarly H1-Mod exists for CoD: Modern Warfare Remastered. I’d be interested to hear which ones you’ve tried and how active the community is. They don’t need to be currently active or a replacement for a game’s existing multiplayer services. It could be something like Zandronum which allows you to play the classic Doom with friends. Most of these services don’t contain DRM which is always nice.