But that's the only way to play this game on a handheld at present and don't you have to buy a Switch 2 anyways? You don't even need to buy the license again if you already own one for Windows or Steam while you would have to pay for the license and expansions if they ever come out for the Switch 2. The Ally trounces the Switch 2, so why play on an inferior device when you can already play on the Ally that has native support for the game without SE needing to touch anything? They would have to commit a lot of resources for the Switch 2 port since the CPU isn't even x86 (ARM) based like PC's and the XBOX/PS4/5 and would need to be emulated and that hurts performance over the already weak hardware vs the Ally.
You can install Windows 11 on the Steam Deck and Steam even provides official drivers too, therefore making it legitimate.Also, S-E doesn't support FFXIV running on Steam Deck. That's because Steam Deck is a Linux, an OS that is not officially supported. You even need to use emulator and some anti-TOS tools to be able to run it on Linux.