Very yes. Not only are Steam and Proton usable on distros aside SteamOS, improvements from those regularly flow upstream into Wine, DXVK and also the Linux kernel itself.

@Kaldo @sdx Even though #Valve is maintaining #Proton, which is based on #Wine, I think projects like #DXVK and #GalliumNine would not exist or have come this far if it weren't for Valve.

I think Valve's contribution to the #Linux world is very indirect, but cannot be denied.

Lets take the imaginary program Y. It is free open source software with the GPLv3 license. If Valve wants to include Y in SteamOS, they are free to do so. Any time Valve makes changes or fixes to Y, they are legally required to provide the source code of their changes, as stated in the GPL license included with Y.

A lot of programs have this license (or a similar one), which forces corporations to contribute back to FOSS projects.

Some Valve-made components in SteamOS are truly "SteamOS only", but a good amount of fixes to non-Valve programs are submitted "upstream" (to the original project). Due to the nature of Linux, it might be possible to copy the few non-foss components in SteamOS and directly use them in another distro.

Alongside forced contributions due to licensing, Valve contributes a lot of code to "gaming" programs on Linux, such as Wine or DXVK. They also make some SteamOS components FOSS, including Gamescope for example. Valve is (currently) doing a lot of work "for the community" rather than for direct profit.

Mainly their creation of Proton, and contributions to DXVK and WINE have helped Linux gaming become possible on any distro.

Before SteamOS could become a thing Valve made HUGE effort to make Linux useful for gaming. All the games everyone can now easily play on any x86 Linux distribution - that was possible, in a big part, by Valve efforts. Driver improvements, compatibility layers (not just Proton, but also improvements in the upstream wine), etc.
And they do continue the improvements, not just for their own Linux systems.

Almost nothing Valve has worked on is only for SteamOS, other than packaging and distributing SteamOS itself. They've upstreamed kernel patches, RADV patches, KDE patches, etc which affects all desktops. Not to mention the open source tools like Gamescope and Fossilize, the latter of which is used automatically on all Linux PCs playing Steam games, and their contributions and funding to Wine and other projects. Even the new Steam big picture UI, which was initially only available on SteamOS, is now broadly available.

It's no exaggeration to say that Valve is carrying Linux gaming these past few years. It has been a downright renaissance.

Since Proton can be used on any other distro, every distro is positively affected by Valves development/improvements of it.