

When I started my home server was an old laptop, eventually it became an old desktop, and now it’s server specific hardware. My recommendation is use whatever you have at hand unless you have specific reasons. I went from laptop to desktop because I needed more disk space, and went to specialized hardware for practical reasons (less space, less electricity, easily accessible hot swappable hard drives). But for most of the stuff I have there an old laptop would still be enough, heck, a raspberry pi would be enough for most of it.
What’s your GPU? Nvidia’s you will need to use the proprietary drivers, AMD it depends on how old it is but newer ones should be good with the default driver.
From the issues you mentioned on Ubuntu I think it’s likely you have an Nvidia since it doesn’t play completely nice with Wayland all of the time, which sucks because X11 is halfway out of the window.
Another thing I think you probably know but just in case, you can install different Desktop Environments on the same distro, no need to change distros for that. So you could install Plasma (and yes, Plasma is KDE) or Gnome on your existing mint installation.
Honestly I think Mint is great for beginners and if you’re happy with it there’s no reason to switch. One thing I always recommend though is keeping
/home
in a separate partition so you can reinstall or switch distros without deleting your data.