Sevoflurane is a tool for running Windows Steam using CrossOver or its own bundled Wine (Dormison). It replaces Steam's Chromium UI running through Wine with WebKit running natively, and forwards your Steam notifications as macOS notifications. It also sets Discord Activity.
When used with the bundled Dormison, the new version can now also download and launch your macOS games, with working achievements, using Valve's existing SteamPlay compatibility tool. This is similar to NotProton.
How is it different from NotProton?
NotProton works by loading its library into Steam and patching CrossOver. Sevoflurane doesn't inject anything into Steam for Mac or patch CrossOver.
Games interact with the Windows client. This means Sevoflurane is doing the reverse of what NotProton is doing, where games interact with the Mac's Steam.
How is it different from CrossOver?
It can run games through CrossOver unchanged, or it can use its bundled Wine fork. If using the fork, you get resizable windows for most games, upscaling, Game Mode, mouse acceleration off, and FPS overlay.
Download and more info:
https://github.com/kageroumado/sevoflurane
The project is free. If a future Steam update breaks something, please open an Issue on GitHub.