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.
Thankfully the lemmy developers are aware of those issues and are working on improvements.
Looks like soon, viewing content will always be done through your instance and links won't take you to other instances. The clunky way to search for communities on other instances if your current instance doesn't know about them yet will get fixed too.
Multireddit style aggregations of communities are also being worked on
Plus these days there is a massive influx of users, once this stabilizes a bit all major instances will be federated and know about communities on each other, so many problems of discovery will get mitigated.
you can make only one account, but it has to be on an instance that allows NSFW. Then you can see NSFW from other instances too.
Many instances are disabling NSFW because it's hard to moderate and the nature of lemmy means NSFW content could come from other instances and be problematic.
I played over two hundred hours of the steam version on Proton 8