I’ve had games with native Linux versions on Steam break more times than games I play through Proton

How many of these games target a proper Steam Linux Runtime? My guess is none and your experience is based on ancient Linux versions from a time SLR did not exist.

When native Linux games break it has been permanently, because the developers stop maintaining it.

Of course. "Valve refuses to promote it towards developers" I literally wrote that already.

Proton is a hacky workaround, targeting and properly maintaining Steam Linux Runtime is the proper solution but Valve does not promote this, so nearly nobody knows about it, and Lepton could be a properly promoted, directly based on AOSP instead of reverse engineering option, should Valve bring it to x86. That's literally what I wrote already.