Check out distrobox. It's a way to have a Ubuntu (or any other Linux distro) container and allows you to install Ubuntu packages, even desktop applications.
It works great for when you need to install a random .deb file or follow a very Ubuntu specific step by step procedure. I use it exactly for this kind of stuff.
No rebooting needed, integrates fully with the host system, no virtual machine either.
DLSS works fine on Linux, but I don't know about frame generation and ray reconstruction specifically. It could be those two don't work yet.
Yes, this game is like that. This game also has more in depth simulation and mechanics, but it's way less accessible.
One major difference is that RimWorld has a narrator AI that will make up events for your colony to experience, while dwarf fortress tries to simulate a world and the events are most of the time the result of the world simulation.
This makes RimWorld more gamey, meaning dwarf fortress can kind of get stuck in weird or bad situations, and men in black won't magically show up to save your colony. But for many players that's part of the charm!
I played over two hundred hours of the steam version on Proton 8