My brother and a few friends use their Steam Decks as regular PCs no problem. Just need a good hub or dock to cover things like HDMI out, multiple USB ports, Ethernet port, etc. When my brother's desktop PC sh1t the bed, his Steam Deck became his gaming PC, and his laptop was his non-gaming PC.
My brother and I both main Linux on all our PCs, so Steam Deck fit in pretty well with him. Steam Deck comes with KDE Plasma 5 and that's the main desktop environment I run these days, and for my bro it's his secondary (his main is Awesome WM). I've gravitated over to Arch-based stuff within the last decade or so, and the current version of SteamOS is based on Arch Linux, so that's cool too. Steam Deck was a fantastic introduction to Linux for two of my friends who had never really used Linux before. Looking at sh1t like Win10, Win11, MacOS X, and MacOS 11, Linux and BSD are really the only true PC OSes left.
Anyways, I think it would still be nice if people could run whatever OS they wanted on a Steam Deck without issue, including Windows 10 and 11. Some tech sites/channels have already experimented with running Windows OSes on Steam Deck, but I think Microsoft should officially support the device. Then again, the Steam Deck being mostly stuck on Linux has really helped the Linux side of gaming. The driver and game support is only gonna get better from here, as the Steam Deck gains in popularity. What helps Steam Deck ends up helping Linux on the whole. Valve too deserve props for a lot of the Linux work they've done over the years, and continue to do.