This may not be a Linux specific problem as I had the exact same issue earlier with Windows 7 and it's one of the reasons I installed Linux in the first place.
The specific game I'm trying to play is DayZ but it may not be issue specific to this game. It worked flawlessly untill this point. I had made no changes to anything. Basically when I try to launch the game it starts loading up normally and then just apparently quits and the "Play" button goes back green. No error, no black screen, no freezing or anything. It just stops launching the game.
I've tried checking the integrity of files, deleting downloads catche, disabling steam cloud, removing launch options.. nothing. Almost like it gets blocked by firewall or something. However I feel like it may be an issue with steam itself or then it's a hardware issue (I've got really old PC)
Few things I've noticed that may or may not be related:
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When opening up steam it almost always used to download some updates first and check the integrity of them or something. Now it doesn't. It just opens up Steam. When I click "check for updates" it says everything is up to date.
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The firmware updater shows available updates for my SSD and HDD but no option to update. I also tried with
sudo fwupdmgr get-devicesbut it says "UEFI firmware can not be updated in legacy BIOS mode See https://github.com/fwupd/fwupd/wiki/PluginFlag:legacy-bios for more information."
- In the privacy settings it says "checks failed" and gives me this message:
- I've tried reinstalling Proton BattlEye Runtime but it wont let me uninstall it and says "missing shared content"
Yeah, snap packages have a tendency to break everything, so avoid them like the plague. You should be able to choose what repo you install from in the Ubuntu app store by clicking the dropdown in the top right of the app's page (which defaults to snap if one is available), and selecting something else. I can't remember what the options are, but for a native install you're looking for something like ".deb", or "Ubuntu repository", or "apt", something of the like. You could also install flatpak and set up flathub so you can get apps packaged as flatpaks (which are kind of like snaps, except they actually function and generally work well for most applications). Not sure if you can get flatpak working with the Ubuntu app store, but it works with Gnome software stores for any other distro out of the box (like Fedora and Nobara). Ubuntu is owned by Canonical, who manages snaps, so they have financial motivation to shove them down their user's throats (which has been met with much dismay by the Linux community).
Snaps and flatpaks are essentially meant to be portable formats that are packaged with all of their dependencies inside their own sandbox so that they function the exact same when installed on different distros. This has great applications for compatibility (you can install the same package on any distro instead of compiling your package for multiple package managers and distros), and security (the sandboxing serves as a layer of isolation from other apps. Flatpak does this pretty well, but snap has tons of problems.
If you're ever at the point where you want/need to install a new OS, I'd recommend switching away from Ubuntu to avoid the headaches. Linux Mint is a common recommendation if you want to stick to a system that's similar to Ubuntu (it's based on Ubuntu), but my personal recommendation is something Fedora-based like Fedora Workstation or Nobara. You can find tons of info in this community on what different distros are like, and you'll see that there is no one "best" distro.
If you ever run into any other problems though, this is a great place to ask for help. One of the many great things about Linux is that much of the community is very knowledgeable about how to do/fix practically anything; and many of those people are just happy to help someone so they can enjoy their switch to Linux. There's also AskUbuntu, the Arch Wiki, Fedora forums, etc. that are available for whichever distro they are tailored to.