Launchers

Lutris – allows you to install and run games from the Humble Bundle, GOG and Steam launchers. A free and open source game

Heroic Games Launcher is an open source game launcher, access to their Epic, GOG and Amazon games

ScummVM is a program that allows you to run various games, provided that their files are available (which were not developed for your system)

GDLauncher is a simple but powerful Minecraft custom launcher with a strong focus on the user interface. Free and open source game