Considering Microsoft is dropping support for Windows Mixed Reality devices with Windows 11 24H2, effectively sending millions of otherwise perfectly fine VR headsets to landfill with no recourse. I can see them releasing a handheld with a "custom" version of Windows that allows users to install Steam, GOG, Epic, etc... then bait and switch with a future "feature update" that makes compatibility "too hard" to support or a "security risk". Maybe the desktop mode is a "developer only" option that gets disabled, or you have to enable third party apps like in windows 10 S and that ability gets taken away. I wouldn't put it past Microsoft.
Maybe I'm just peeved at Microsoft for deciding that my VR headset will be E-waste even though the hardware is fine, or ignoring the concept of user consent by enabling OneDrive cloud backups for local folders by default while basically forcing you to create a Microsoft account to install Windows if you don't know the right sequence of arcane f-ing rituals to create a local account. But I don't trust them...
Because it's based on fedora atomic it uses rpm-ostree, which lets you layer packages to persist between updates. Good for stuff that isn't available as a flatpak or doesn't work as well when installed as a flatpak. Beyond that not much, maybe if someone doesn't trust Valve with their OS?
On SteamOS you can still kind of have non-flatpak packages persist by using distrobox. It's still a sandbox, just one that has a bit more latitude in what you can install than a flatpak.