UMU

Unified Launcher for Windows Games on Linux (Open-Wine-Components) —
essentially a copy of Valve’s Steam Runtime Tools + Steam Linux Runtime,
modified to run outside the Steam client. It makes Proton usable
by any launcher: Bottles, Lutris, Heroic, Rare — no Steam install
required.

How it works:

• umu-run wraps a game exe with the same runtime Proton expects;
  config via WINEPREFIX, GAMEID, STORE, PROTONPATH env vars
• GAMEID + STORE are looked up in the umu-database; matching
  protonfixes scripts are applied to the prefix before launch
• PROTONPATH=GE-Proton auto-downloads the latest GE build; default
  runner is UMU-Proton (Valve’s stable Proton + UMU compatibility)
• Steam Runtime lands in ~/.local/share/umu

The point: one standardized way to “run it like Steam would”, so every
launcher benefits from the same fixes. Adopted by Bottles in v66.