PopOS is currently using modified GNOME on Xorg. It’s impossible to get mixed refresh rates on Xorg/X11 (which is the legacy display protocol) and with your setup you are pretty much stuck with Wayland (the modern display protocol still, still progressing as a platform) - which is what you tried first if you used Nobara, whether it’s KDE or GNOME.

Note that PopOS 24.04 (that will be released this fall iirc) will in fact run on Wayland with all new Cosmic desktop (it’s first full DE written from scratch since like 90s) and promises great NVIDIA support - which can definitely be the case given recent updates.

Now on the flickering issues that you experienced, they’re specific to the NVIDIA driver and are just being ironed out. There is the new explicit sync Wayland protocol, new NVIDIA driver, patches for XWayland, patches for Mesa, maybe something more. It still might require pulling something that didn’t make it to stable distro repositories, but I think Nobara provides that and for sure will when 40 will get released soon-ish. I don’t have NVIDIA GPU, but I saw conversations on Nobara Discord and they help each other get NVIDIA going so maybe ask there.

The time frame is a bit of a problem here. If you want to avoid tinkering, hold for a little longer and in few months most distros (that ship a Wayland session) will most likely just work with your setup. If you want it now, feel free to get your hands dirty and find a way to run NVIDIA on Wayland with explicit sync support.

Popping in to give an update before calling it a night!

First of all, thank you for all the help! I’ve been reading through all the comments here and trying a few things out. The first thing I tried was switching the default desktop environment from the default Gnome to KDE. I much prefer KDE to Gnome since I have experience with it on the Steam Deck, so this is the solution that I had the most hope for. Sadly though, things are much worse in KDE. Unlike in Gnome, KDE has the terrible screen tearing that was mentioned in X11, but is still similarly unable to support running the monitors at different refresh rates. Since a lot of the comments here mentioned Wayland though, that was my real end goal in getting KDE installed. Unfortunately, witching over to KDE Wayland, things became significantly more unusable and it was about the same experience I had while trying to install Nobara. Both displays were totally unresponsive for seconds at a time and I was only able to interact with things during brief moments when they would stutter along instead. This was pretty painful to log back out of and was an overall mess like a couple of you had mentioned it might be.

I went back to Gnome after this. Since KDE didn’t seem to be they way forward, I figured I might as well try enabling Wayland on Pop_OS’s built in solution. Wayland support was hidden by default on NVIDIA as mentioned, but one quick config edit later and the option appeared. Things seem to be going much better now! I’m running Gnome Wayland right now and while things aren’t flawless yet they’re significantly better than before. Both monitors are working at their full refresh rates now without any screen tearing or flickering. As for gaming, so far I only have Helldivers 2 installed running through Proton, and performance is about 8% worse than in Windows on the same graphics settings while on the ship. I am also getting an odd visual bug where the in-game menu looks like it opens and closes very quickly every once in a while. It’s not actually open or intractable though, it’s more like the game randomly displays a single frame from when I did have the menu open to change the graphics settings. Tomorrow I’ll try enabling Proton experimental and see if that fixes anything, and also try installing some more games.

I’ll come back again to give an update on how things are going then! I’m still lacking HDR and there are other bugs that look like they need to be ironed out, but I’m much more optimistic about this than I was before. I think I’ll keep dual-booting for now, at least while I’m still trying to get everything working properly, and hopefully that next version of Pop_OS brings HDR support. For now, it’s at least nice to know that different monitor refresh rates are working.

Unfortunately Nvidia is just going to give you problems on Linux…

Someone correct me if I’m wrong but if you’re using stock Pop_OS it uses xorg by default as the compositor which iirc has issues with multiple monitors on different refresh rates. You can edit your .config file to enable the Wayland compositor and give it a try and see if it works!

So yesterday, I tried Bazzite os, and it’s pretty good. Works perfectly with Nvidia GPU. You have to use x11 instead of Wayland. So far, I’ve tested BF1 and Hell Diver 2. Experience is excellent, with no lag whatsoever. It’s the first time I’m giving Linux a proper shot. However, I will need some advice on optimising it. For example, fan control or any other tips/tricks I can get.

(I had app flickering issues, and changing to x11 fixed it)

Dual monitors are working perfectly with 165Ghz refresh rate.

You are likely using X11. X11 treats all enabled displays as one “screen” and therefore different refresh rates will have issues (as will VRR for example).

Wayland is the way to go, but the NVIDIA drivers are still buggy with Wayland. Pop!_OS currently uses a desktop environment based on an outdated version of GNOME, so it probably won’t be amazing under Wayland.

I’d recommend using a distro with a recent version of KDE Plasma as it has non-experimental support for VRR and great support for Wayland. You’ll also want an up-to-date kernel and the latest NVIDIA drivers. I recommend Fedora KDE Spin or openSUSE Tumbleweed. Installing NVIDIA drivers is a little bit more involved (search for “RPM Fusion NVIDIA” for Fedora), but very doable.

I personally switched to an AMD GPU because of the issues with NVIDIA, but NVIDIA support is improving so you’ll probably be fine.

You will have to use wayland to run monitors at different refresh rates without tearing. You will also need wayland for HDR. It’s still not working perfectly yet, but there is a lot of work being put into it.

HDR support is still very much incomplete, Valve is driving that effort and something should be available Soon™ maybe later this year or next.

You’ll want a rolling release distro of some sort to take advantage of the most recent work on display tech. Check out Arch, Fedora, Nobara, Bazzite, etc - they’re all much more current than Pop (which is based on Ubuntu and cuts stable releases every couple of years.) Use Wayland and pipewire to take advantage of the modern display and audio stack and more modern features (VRR, HDR) should “just work” when they’re implemented and released.

Please do an update later on. I also want to try out Linux gaming. Gaming is the reason I keep going back to Windows.

Like you I’ve tried to game on Linux and each time have had to go back. I really want it to work, and to be fair, it DOES work. I love my Steam Deck and it’s proof that with enough tuning you can get a good experience.

However if you want to get more than a game just running, that’s when you have some issues. Like you I had the X11 multiple monitor issue people describe. Wayland is the fix these days but there were still issues using both different high refresh and VRR at the same time (may be fixed now).

My current issue is trying to get gamescope running when launching games from steam on Fedora 40. I have the flatpak of each and guides say it should just work, but every time I use gamescope as a launch option nothing launches. I imagine there must be a log somewhere but I don’t know where that is. I found some open bug reports that say gamescope just broke a few versions ago with Steam, who knows.

The only reason I need to use gamescope is that there is no AMD control panel, so no way to get FSR. This is a lower end GPU and I really need FSR for this particular game to run well. This is the biggest issue IMO, with only basic GPU drivers the community has to figure out how to implement the latest gaming features on their own, which means it is years behind. The VRR/High Refresh multiple monitor issue for example is something windows was doing with ease several years ago and Linux is getting it now.

So you have to give up a lot of multiplayer games, and you have to be OK with just running the game, not anything modern like DLSS or frame gen, or whatever is cutting edge. For this reason I can still only recommend gaming on Linux if you’re on a Steam Deck, or if you’re a techy person who mostly plays single player titles. Anything more and you will be messing around more than playing.

try Ubuntu