Closer to the EoL time, someone is going to release a version of Linux that is basically windows, with a super locked down interface etc to make it so newbies can install and use with zero CLI or setup.
Or at least some serious consumer-grade onboarding.
Presumably it will have reduced functionality to make it as stable as humanly possible too.
And they'll probably become one of the larger distributions until people get the confidence to "upgrade" to a more complex one.
There's nothing really special about the OS on Steam Deck that you can't get with any standard major Linux distro with Flatpak, Proton, and KDE installed. It's all free and open source software except for the Steam client itself. It's not that hard to set up a system just like Steam OS. If you're a "power user" who's messed around in the Windows registry, you can customize and set up a Linux distribution.
I think they're working on it, I could have sworn they said they were but a quick Google search shows nothing for me..
I saw someone posted bazzite as an alternative to steam os, but I'd just rather wait for whatever valve puts out at this point. I trust them to make it happen a little bit too much lol
If they can get a version that just runs all Windows programs (not just games) out of the box without user modification then great. I'd consider that to be an actual Windows replacement.
If all you're running is a browser and some light office suite use then great, Linux can do that now. Otherwise what people saying "just switch to Linux" are really saying is "stop using your PC".