At some point recently, Valve updated the Steam Beta Client with a change to the way Proton is enabled making Linux gaming easier. Quick note for newbies: Proton is a compatibility layer to run Windows games on Linux systems available on Steam.
For some context here: originally, Proton had an option to enable / disable it globally. That was removed with the Game Recording update last year. That made sense, because people kept somehow turning it entirely off and now it's required by Steam.
Currently, there's still an option in the stable Steam Client that you need to manually check to enable Steam Play (Proton) for "all other titles". This is something of a leftover from when Proton was initially revealed, and only worked for a specific set of games on Valve's whitelist. It now covers what Valve set by default for Steam Deck and SteamOS verification.
What's changed is that at some point in the recent Steam Beta releases, is that "for all other titles" option is gone. I've scrolled back through changelogs and not seen it mentioned. So now, Proton is just enabled properly in full by default in the Steam Beta like shown in the below shot.
This is a good (and needed) change that I'm happy to see. There's often confusion when people try to run Windows games on Linux and end up with no install button because Proton isn't turned on for all titles. The below will soon be a thing of the past:
To be clear, this is not setting Proton on every game by default, it does not override Native Linux games. It's just making Proton available by default.
It's just one more little nuisance niggle removed, to get people playing games on Linux even faster
That would be something I'd put next to the adverb finally.
The only thing preventing it from wider use outside of Steam is the relative lack of third party launchers that support using Proton.
Heroic does support it outside of Steam now, and I believe you can use Umu as a launcher from Lutris.

For a short, exciting moment after reading the title, I thought that Valve was letting players use Proton outside of Steam.
That would be something I'd put next to the adverb finally.
You can already use proton outside of steam
By the way, what version of Proton will be set as default in this state? For those familiar with Linux and Proton, it's not too much trouble to switch to the latest stable Proton version with each annual update. But for users who aren't aware of this, couldn't they potentially get stuck with an outdated Proton version a year or more down the line?