I am most familiar with Debian but only headless. What would be a good choice of desktop environment? I’m looking to switch over the only windows computer in my house to Linux, it is primarily used as a home theatre and gaming PC.

Desktop environments are a matter of taste, but since you asked, I like KDE Plasma. I think it would be pretty comfortable for someone coming from Windows.

It's not the default on Debian, but once you install it, you can choose it next time you log in.

https://wiki.debian.org/KDE#Installation