It’s very easy to bypass the requirements. Just search “how to bypass Windows 11 install requirements”.
I’ve installed it on a a handful of machines that didn’t meet the requirements and haven’t had any issues with them other than one not being able to launch a game because the anti cheat needed newer TPM 2.0
Armbian with CasaOS
I can’t speak on moonlight specifically on the pi 4, but it running steamlink on wasn’t bad on it, so I can’t imagine it’s would be any worse than that for moonlight.
Wired Nvidia shield TV has been my best experience when it comes to both moonlight and steam link out of all of the devices I’ve tried it with.
There’s a docker image called wg-easy I use with a nice web interface.