UMU comes from GloriousEggroll who is well known for making protonGE that’s required to run several games on linux/deck.

It’s not a launcher by itself, but rather something that can be built into other game launchers like Heroic, Lutris, and Junk Store. Right now most all steam games that don’t have anticheat run great on deck without any tweaks. However many of those same games don’t run by default if you install them from Epic/GOG/etc using one of the previously mentioned launchers. The games often require additional windows components to be manually installed with winetricks/protontricks, and many have lesser performance than their steam counterparts.

UMU is supposed to help other launchers have comparable compatibility and performance to what we see in steam native games. This project will hopefully improve the 3rd party launcher experience a lot.