Yeah, I probably wouldn’t buy a new laptop for a server, but it’s a great way to re-use what would otherwise be e-waste. I have a 20 year old laptop running as a server, currently just for FoundryVTT, but it works great. 4GB of DDR2 ram, Intel celeron dual core cpu. I stuck a new ssd in it (old hdd died) and it works great, as long as I don’t run any graphical interfaces while I have the server running. One ram stick was bad, but DDR2 cost me about $11. Total hardware cost was around $50 USD.

Thinking about just removing the lid entirely, since I don’t use it graphically (I can hook up a monitor if absolutely needed).

I have used gnome, plasma, and xfce and they are all fine. I prefer KDE personally but they’re all going to do what you need to do. It’s all down to personal aesthetic preference, and picking one won’t hinder you in any real way. KDE to me just looks super nice out of the box for my taste, and I like the customization.

I love Debian. Been using it on my laptop for over a year. Some specific drivers are a little fiddly if you have nvidia graphics but it’s not too bad, lots of good info on the debian wiki.