One thing that would be good to check is to make sure the Nvidia proprietary driver is actually controlling your video card.

Run

sudo lshw -c video

in the terminal, and make sure that under “configuration” you see “driver=nvidia” and not “driver=nouveau”.

Also make sure there’s only one entry that comes up. I’m pretty sure your CPU doesn’t have an iGPU, but good to make sure.

Try setting proton to version 7 in steam. I had a similar issue and it was down to having an older gpu that wasn't compatible with stuff the newer proton releases were doing.

Sounds like a driver Nvidia driver issue. Have you tried running a natively supported game like Counter Strike?

See if you can update/install the nvidia proprietary drivers and see if anything works.

See also if there's a recommended diagnostics program to see if you can get more clues if the above doesn't work.

In cases like this, because of the simplicity, I suggest installing PopOS! Nvidia ISO. Chances are, with that hardware, that it will just work. Good luck bud.

You may have the GPU drivers installed but are they active? Look in "Software & Updates" on the Additional Drivers tab and see which drivers are active.

Installing the drivers is not enough, you have to select them to use them too.

If the latest drivers are active then you may need to think about switching to a legacy version (you have a pretty old CPU and GPU by current standards; newest drivers are not always best). You may also want to look at using older versions of Proton than the latest for similar reasons - there may be features and changes in newer versions that are just not going to work with your set up or your set up just isn't tested to work with.

Try run steam from terminal, it will show more logs about the error, this is my best advice for now since I don't use Nvidia for a while.

What format is your hard drive or drives? Ext4?

Imo distro doesn't matter very much. Your best bet is to try either Lutris or Bottles in order to manage your games easier. Then you just need to install dependencies and the games should work. If not, try other wine versions, proton, proton-ge etc

Are you on X11 or Wayland? Steam has crap support for Wayland

There are a lot of interesting things in your post.

First, League typically doesn't work well on Linux because Riot doesn't care about Linux users. If League is going to be a deal breaker, I'd recommend getting a dedicated Windows system for the best time.

Second, your CPU has a known hardware bug with C-states. If you've been noticing your computer freeze often under Linux, disable C-states in your BIOS.

Third, are the games you're trying to launch purchased through Steam, purchased through a different store, or pirated?

Are you able to play any of your games, or is it just these few that have been giving you trouble? If it's every game, you may not have the nvidia driver or vulkan installed. Just to be sure, you can try running nvidia-smi in a terminal, which will show you which driver the system is using. If you are unable to run the command at all, you'll definitely need to install the nvidia driver

That's odd, I installed Nobara as my OS and almost any game is just install and click play and it plays flawlessly. Using both steam to install and Heroic Launcher (which you could try) that has the capabilities to get the games you have on GOG, Epic and Amazon Prime*. Don't forget that in steam you need to enable Linux/Proton in settings.

Otherwise ProtonDB is a great resource to see what games run on Linux, how well they run and how each person ran the game.

https://www.protondb.com/

Edit: I do believe getting a dedicated gaming distro does help as it has a lot of necessary tweaks pre-configured. For that I'd recommend, Nobara, Garuda or PopOS!

I started using Pop OS at the start of the year and have managed to play the vast majority of games including Baldur's Gate 3. My hardware was similar to yours (though I've recently upgraded): 3700X, 1080Ti. Downloaded the version of Pop with the Nvidia drivers and ensured Steam Play was enabled for all games (to automatically utilise Proton).

I'd suggest trying the other Nvidia driver versions, as one of the other ones might work better with your 1070. Seem to recall I accidentally switched to one of the other versions Pop offers and had issues so maybe playing around with them will get some games working

Make sure you don’t have “amdvlk” installed rather than lib32-nvidia-utils

https://wiki.archlinux.org/title/Vulkan

Arch wiki might not have correct details of package names for Ubuntu, but it’ll put you on the right track.

Is it a laptop ?

I haven't used Ubuntu, but I had a similar setup to yours in the past, and on Archlinux I couldn't run any game until I installed 32 bit nvidia drivers (on arch the package was named lib32-nvidia-utils), and that's my first instinct - maybe you don't have 32 bit drivers installed?

Now, as I haven't used Ubuntu much I'm just going off of online reference so there commands might not be 100% correct, but try doing this:

sudo dpkg --add-architecture i386 to add 32-bit app support

sudo apt install -y libvulkan1 libvulkan1:i386 to install the vulkan drivers, including the 32 bit one. I'm not sure if this will have the same effect as lib32-nvidia-utils package on Arch though or if it does the same thing, but hopefully it works.

As for League, it does work on Linux quite well, but the installation is a little bit unusual. The gameplay though is literally the same as on Windows, no performance loss there at least in my experience.

I’ve played most of those games on Linux and they work out of the box on my EndeavorOS setup with AMD. You may be missing some drivers or libraries specific to your setup.

Also make sure the steam Linux runtimes are installed

It should normally just work, I reccomend nobara it got it's 39th relase yesterday and it is THE gaming distro

I'm no help here, but I have been thinking strongly of converting an old windows box to Linux gaming with steam, so I'm hoping someone can help OP and I can pretroubleshoot my own transition. Steam has their own debian-based OS, right? I was planning on falling back to that if proton didn't work