RetroArch - RetroArch is a frontend for emulators, game engines and media players.
Roll20 - Roll20 is a suite of easy-to-use digital tools that expand pen-and-paper gameplay.
Batocera.linux - Batocera.linux is an open-source and completely free retro-gaming distribution that can be copied to a USB stick or an SD card with the aim of turning any computer/nano computer into a gaming console during a game or permanently.
Astral Tabletop - Create, host, and manage your tabletop role-playing games — online or in person
Playnite - Source code generated using layoutit.com
D&D Beyond - Official online toolset for Dungeons & Dragons tabletop gaming