It didn’t work out in the end, though. I was able to install mangohud and it did appear in the game settings in Lutris, but it was greyed out so I couldn’t activate it.

So, I don't use Lutris, so I can't help much there, just Steam

sorry. I don't know how it detects whether mangohud is present. There, it isn't a checkbox, but a text field where one can specify options to be passed to the program run.

I don't have Steam on the machine I'm on right now, so I can't take a screenshot of that, unfortunately. I believe that that field is in the same place on Windows and Linux, though

not something Linux-specific.

searches

Here's Steam's help for setting the text:

https://help.steampowered.com/en/faqs/view/7D01-D2DD-D75E-2955

That being said, rather than trying to first run the game under Steam or Lutris, I'd try to run vkgears and glxgears from a virtual terminal program, whatever KDE uses

like, there'll be some KDE terminal app. searches Looks like it's called "Konsole". That'll cut out Lutris and Steam from the equation. If you can't run 32-bit or 64-bit OpenGL or Vulkan stuff with hardware acceleration, then that's a good candidate for being the cause. But if you can, then no sense in digging further down that path. Like, I'd just run, in Konsole:

$ MANGOHUD_CONFIG=full mangohud  vkgears.x86_64-linux-gnu
$ MANGOHUD_CONFIG=full mangohud  vkgears.i386-linux-gnu
$ MANGOHUD_CONFIG=full mangohud  glxgears.x86_64-linux-gnu
$ MANGOHUD_CONFIG=full mangohud  glxgears.i386-linux-gnu

All of those should show a window with spinning gears, and none of them should say "llvmpipe". If they have "llvmpipe", that path is using software rendering, very probably because you lack 3D drivers for that path.

Uh...and just to clarify, so, Windows has a 3D API called DirectX. Linux doesn't natively have this. Most Windows games are written to use DirectX. So when WINE or Proton (Proton being Steam's version of WINE) run, they map DirectX calls to OpenGL or Vulkan, which are native to Linux. IIRC, different versions of DirectX have emulation targeting either OpenGL or Vulkan.

I think that Kubuntu has the same packages as regular Ubuntu, if I understand aright how that works

it's a flavor of Ubuntu rather than a distro derived from Ubuntu.

So, assuming that to be the case, this should be a list of Kubuntu packages.

https://packages.ubuntu.com/

I don't see lib32-amdgpu. Hmm.

looks further

Oh, I'm sorry. I was running a newer version of AMD's drivers than what they ship with the distro on that system. I'm afraid I misinformed you. Apologies. There is no lib32-amdgpu

they renamed it to that in a newer version of the drivers, I guess.

checks on another system

Here's a vanilla Debian trixie system. And...yeah.

$ sudo apt install libdrm-amdgpu1:amd64 libdrm-amdgpu1:i386

I believe that those will pull in both 32-bit and 64-bit 3D drivers for OpenGL, if you're using an AMD GPU. Those are in Ubuntu (Ubuntu Resolute, version 26.04).

https://packages.ubuntu.com/resolute/libdrm-amdgpu1

And for Vulkan...

$ sudo apt install mesa-vulkan-drivers:i386 mesa-vulkan-drivers:amd64

And they're present in Ubuntu Resolute as well:

https://packages.ubuntu.com/resolute/mesa-vulkan-drivers

That's mesa-vulkan-drivers package isn't specific to AMD GPUs, but it looks like it should pull them in.

If you're using an NVidia GPU, I'm afraid that I don't have a system handy to check on.

Every time I start up, the KDE Password Manager launches. And until I’ve entered my kernel password there, neither the Wi-Fi nor the browser works. That wasn’t the case until recently either.

I also don't use KDE, sorry, so I can't add much there.

It's possible that KDE has some sort of keychain manager that it stores your Wi-Fi passwords in, in which case it probably encrypts the passwords using your keychain password. I think that they call their keychain manager KWallet. If you're not online, that'd explain your browser not working.

searches

This is ten years old, so the KDE UI might have changed, but:

https://askubuntu.com/questions/284770/how-to-disable-kde-wallet-and-have-remember-password-working

I solved this issue by going into the network manager settings by clicking the wifi/network icon in the taskbar > Settings icon, and then from the networks screen that appears, I right-clicked my connection, clicked edit, and then under the "General configuration" tab, ticked the "All users may connect to this network" check box. When I restarted my computer, I wasn't asked to enter the kwallet password and connected to my network automatically.

Works for me BUT I also need to specify "Store password for all users (not encrypted)" in the "Wi-Fi Security" tab otherwise it doesn't work.

https://discuss.kde.org/t/kwallet-blocking-wi-fi-setup-is-pushing-new-users-away-from-kde-plasma/41854

Recently, both my father and my wife tried using Linux with KDE. When they attempted to connect to a Wi-Fi network, a KWallet prompt appeared asking them to create a password. Neither of them understood what this was, or why a “wallet” was required just to connect to the internet. They got stuck, couldn’t finish what they were doing, and eventually gave up and went back to Windows.

That's recent, so it sounds like, at least on some systems, it defaults to using the KDE keychain manager to encrypt the passwords.

If I try to view additional drivers under ‘Software & Additional Drivers’, the page just keeps loading and loading, and even after 20 minutes nothing is displayed. Only when I go via ‘System – Drivers’ do I get to these additional drivers.

Yeah, same problem

I'm afraid that I don't use KDE, so I can't provide much help there.

If nobody answers here, you might also try !linux4noobs@programming.dev on the WiFi thing and maybe the KDE package installation thing, since it's not really a gaming question.