Well, you basically are possible to install Windows on the steam deck, since it only is a computer, valve even has drivers for windows online. You might even be possible to split the ssd for steam os and windows, but I heard sometimes that Windows messes up the bootloader and then steamos will not boot that easily again… But I never made any experiences with windows on deck. I guess you will lose some performance, since the processor in the ally is better, but it might be worth a shot. If you decide to do so, keep in mind, that you perhaps need a windows key for windows on the steam deck

P.S. there are plenty of guides to dualboot windows and steam os or to fully replace SteamOS with windows

It would most likely need Itch.io, EA and Ubisoft to produce working linux apps working on the steam deck. If this works in the distant future you would be able to add them as a non-steam game and perhaps even start games with proton layer via ea desktop / ubi connect etc

The Steam Deck is my personal ultimate handheld. I wouldn’t want to miss it. You will get better graphics/performance on xbox or ps5 in many titles - no doubt. But I would guess you have a few games on steam and since you like handhelds - I’ve never felt more comfortable on a handheld before. But it is a bit heavy in my opinion for constantly holding it up. Playing in a state, where you can rest your hands on a surface works best.

Asking in the steam deck subreddit will most likely result only in arguments for the steam deck. But I owned every device you listed and only really miss the ps controller.

It is possible to dual load windows and steam OS. But I would say, since the softwares from the legion go or ally are configured and optimized for each processor used. I don’t believe it would work. Perhaps some features work but others could be breaking the software or even bricking it by falsely overclocking the deck.

Always look into ProtonDB - The community over there is almost always the most frequent and newest source for stability on steam deck

https://www.protondb.com/app/1337520

I guess no, there are some emails between Steam and some users saying parts from the SD-OLED are not compatible with the SD-LCD. Since the Oled screen is thinner it made more place for a bigger battery. I would say the bigger battery would not fit into the old deck. But for a hundred percent answer we’ll have to wait for some tests regarding this.

3.5 is not available in beta it is alpha, so you would need to change to the preview-channel and it should work.