Proton

Valve’s compatibility layer for running Windows games on Linux through
Steam — a Wine fork plus the pieces games actually need, bundled and
versioned as a “compatibility tool”:

• DXVK / VKD3D-Proton — translate Direct3D 9/10/11/12 and Vulkan-title
  calls to Vulkan
• Steam Linux Runtime (sniper) container — the environment Proton expects
• Steam client integration: per-game compat tools, controller, overlays

GE-Proton is a popular community build with extra patches. Outside Steam,
Proton historically needed Steam’s machinery — that gap is what UMU
fills, and Bottles v66 now drives UMU directly from its library.