Aww, and I finally just moved over to Linux.

That's not freezing! That's burning up!

Plot twist: The one on the right is the new 4th person.

Not sure why everyone is recommending you hop distros to fix these issues. Distro choice (at least among the more popular distros) rarely has any affect on gaming performance, it's usually whatever version of proton you're using that's more likely to affect performance when playing a game.

Starting with issue 1:

As someone else said, enabling GPU acceleration is likely to fix this issue. I had the same issue before and pretty sure this fixed it. You may also want to enable "smooth scrolling in web views" as well (it should be right next to the GPU acceleration option).

Issue 2:

• This could be related to issue 1 and may be fixed when you resolve it. Still recommend you read the rest of the suggestions for this issue, it may help in the future.
• Try changing which version of proton you're using. I recommend starting with a more recent version such as 11.0. Stable does not always mean it will run better.
• You can also try Proton-GE. It's a community made version that has some additional features and fixes, most notably some video codex valve doesn't include for licensing reasons. It MAY work better, it may not. I usually keep the latest version installed myself so I can try it if a game is having trouble, even if I'm not actively using it. Easiest way to install this is through a program called "ProtonUp-QT" just note you may need to restart steam to see any new versions of proton you've installed. ProtonUp-QT is only available as a flatpak or appimage on Ubuntu it looks like.

Not specific to fixing this issue, but you can change which version of proton all steam games use by default in steam settings, under compatibility. Changing this requires you restart steam.

Issue 3:

• If you are dual-booting, make sure that all games are installed on a partition formatted for Linux, NOT WINDOWS. Games sometimes run fine from drives/partitions not formatted for Linux, but most of the time do not work. Found this out the hard way myself.
• From a few quick google searches, American Truck Simulator appears to have a native Linux version. If you are using a dual-boot and/or just copied the download from windows, verify the integrity of the files. If that does not work you can always try running the windows version by checking the "Force the use of a specific Steam Play compatibility tool" under compatibility, then select a proton version. It won't perform as well but it's better than it not working. Usually when you do this the game will queue an update to install the windows specific files. If you uncheck the box it will queue another update to reinstall the Linux native files.

I learned the hard way that Linux doesn't always play nice with NTFS formatted drives if you're dual booting, even if it can read them. Just make sure the game is installed on a Linux friendly format drive like ext4 or Btrfs if you want to avoid most issues. Mint usually defaults to ext4.

Pokemon is getting crazy. They're doing regional variants of Rotom variants now?

It might be best to reinstall steam from the repository. It may even fix your issues. Typically 99% of the time if it's available from the repository, you want to install it from the repository rather than from any other source. You can uninstall it from your software manager (app center, snap-store or whatever it's called on kubuntu) then reinstall via the terminal or software manager. The software manager usually pulls from the same source as the command line, so it might be easier for you to use. Just be careful on ubuntu (and it's flavors) because I've seen ubuntu's software manager default to the snap version in the past (which you do not want if you can avoid it).

If uninstalling from the software manager doesn't work, you can try from the terminal. sudo apt remove steam would most likely work. Then just run sudo apt install steam. If for some reason the uninstall returns an error you can search the name of the package with apt list --installed | grep steam then try again with sudo apt remove (package name).

Looks like I may have spoken too soon about the RAM.

I decided to double check your actual laptop specs with a quick google search, and it looks like it uses DDR3L-SDRAM (I would suggest double-checking and confirming this yourself). If that's true, since it's an older type of RAM it hasn't actually been hit by the RAMpocalypse much at all and it's actually pretty cheap. I would recommend 16GB minimum for most modern gaming but make sure your laptop supports however much you decide to install.

Try switching back to the native Linux version (disable force compatibility for proton 11.0 then update the game) and see if that works now. It's probably better to try and get that version working instead since forcing it through proton might be what's making it crash. It will also perform better.

If it's still not launching, try another game that has a native Linux version, and make sure that will launch. You can search for what games have a native Linux version via the Steam OS + Linux filter on Steam. If you don't own, or can't find any games then try Team Fortress 2 or Counter Strike 2 since they're free.

That's unfortunate. Sounds like your computer probably doesn't have enough RAM to properly play the game. The only reason it was likely working on Windows was because Windows will work, albeit very slowly, with max RAM usage, whereas Linux has tools in place (as you discovered) to avoid that, since the system will freeze of RAM usage maxes out.

Sadly there isn't really a good solution to this I can recommend besides buying and installing more RAM, which with current prices isn't the most feasible option. Not to mention it involves opening the computer itself which I have no idea how comfortable you would be doing that.

There are a few things you can do software side to try and maybe make it work, but none of it is simple and it's not guaranteed to work either. This is an issue that swapping distros could help (though it may not outright fix it) as you can install something more lightweight that uses less memory. You would likely also want to change desktop environments as KDE Plasma does consume a fair bit of memory. That being said, I have no idea how easy it is to get Steam up and running on distros designed to be lightweight, so it may involve some additional downloads that defeat the entire purpose of it being lightweight.

Another option on the software side, would be to set up a swap partition. It uses the internal storage drive as a sort of backup memory. It's not guaranteed to fix your issue either, as it comes with some limitations. I don't have experience setting up a swap partition on an already installed drive, so I wouldn't be able to walk you through it. It would probably be easier to reinstall the OS and make sure you create a swap partition at install.

If you do decide to change distros to try and free up some more system memory, some lightweight alternatives I could suggest, based on what you're currently using, are Lubuntu, or Linux Mint using XFCE or MATE. Again, I'm not sure how easy it would be to setup Steam on a lightweight distro so it's up to you if you even want to try changing distros.

• Issue 1: Seems like some people have also had luck disabling both of those options instead, try that as well if you haven't already.

• Issue 2: Glad that one is resolved.

• Issue 3: Are you using mods for this game? If so try disabling/uninstalling all of them real quick to make sure it launches without them.

  If nothing else works you can also try a clean install of the game. This may require that you uninstall it, delete everything leftover for this game in the /steamapp/common/ folder. That being said I'm not sure how big this game is and if you're on a metered connection or not, so I would recommend saving this option for last.

Quick question, how did you install steam? Did you install steam via the repo (something like sudo apt install steam), the app store (I think it's called app center, or snap-store on kubuntu), download the installer from steams webpage, or via flatpak/appimage/snap?