I actually hope that Microsoft doesn't do that. Because I like that stuff like the SteamDeck improves the Linux-based Ecosystem.

If everyone now builds and buys Windows Handheld devices, it probably goes the same route as mobile phones, where a standard Linux or custom ROMs are second class citizen (if you are even allowed and able to use those) and you have to disable or downgrade security mechanisms if you want to install your own operating system.

I would really like if those hardware vendors would come together and improve the Linux gaming experience for their devices.

Nah, it's greatly improving game compatibility on Linux.

I love my steam deck. I'm okay with not being able to play some games on it yet if it means my gaming experience on pc keeps improving too because of it.

Game companies will also be incentivised to add native Linux support if the handheld pc market gets big enough and it's clear the experience is better on a custom Linux distro than something from ms

You can configure Windows not to run the Explorer.exe shell and instead boot directly to Steam in Big Picture mode.

Theoretically anyone could make and distribute an alternative shell designed for this use case, it doesn't need to come from Microsoft.

Agreed, but I imagine there's hesitancy at MS to try again.

MS tried their hand at purpose built mobile OS during the Palm Pilot era, then again during the Blackberry era.

Windows hasn't historically ported to small devices with great success.

Edit: I think there's also likely some awareness (and fear) that the unified mobile PC gaming platform race is nearing it's end, and already has two strong contenders in Linux and Android.