Uhh, why? An API translation layer that you could just run on the host, running in a VM and rendering to a virtualised GPU with no 3D acceleration... Were you trying to make things as slow as possible?

That seems to be obvious to me now

wouldn't be good enough for gaming

Certainly not for anything expecting 3D acceleration. VirGL would help, but that's currently only available for Linux guests.

Uhh, why? An API translation layer that you could just run on the host, running in a VM and rendering to a virtualised GPU with no 3D acceleration... Were you trying to make things as slow as possible?

qemu-system-x86_64 --enable-kvm Unknown.qcow2 -cpu max -smp 4 -m 16384 -device AC97

probably wouldn't be good enough for gaming if I had to guess.

I don't know how GPU stuff works, but my previous experience playing a 90s windows game via wine in a vm was so friggin slow lol.

I will have a look at the cable and see if I can reseat that.

Yes, Fortnite has anti-cheat built into it. So that is a good steer away from using a VM for windows and from using wine and friends.(I have tried Heroic and Steam. Neither seemed to work for Fortnite but that could be me or it could be the anti-cheat.)

I was horrified last-night to read an forum saying that laptops of this sort that last 4 or 5 years are rare and most need extensive repairs long before that. Maybe I have done better than I thought!!!

I could replace the screen and I could buy a new laptop but I am irritated by those options.

IMO, the time (=money) you will spend trying multiple sub-optimal software workarounds is better spent fixing the underlying hardware problem.

In a word, no.
In more words, you can get near-native CPU performance in a VM, but GPU performance for gaming is another matter entirely. The only way you will get native graphics performance is PCI-passthrough, which means either a dedicated GPU for the VM guest or single-GPU passthrough where the host OS is effecitvely unusable (i.e. has no video output) while the guest is running.
Both are a pain in the arse to set up, the latter very much more so.

For most games (aka anything that will run on the Steam Deck), by far the best option is wine/proton + DXVK... The exceptions being anything with invasive ring-0 anti-cheat rootkits or DRM, which will almost certainly not work in wine (unless the developer specifically supports it) and quite likely not in a VM either.
I don't know if Fortnite is one of those, it's really not my kind of game. At a guess I'd say it probably is, since it's a popular "competitive" online multiplayer title and those have a way of attracting scum.

Or dry solder joints, or failing caps, or cracked balls under a mux chip / display driver or the like. Often this kind of thing can be located with a hot air gun and a can of freeze spray...
Whether it can be fixed without specialised equipment depends on where and what it is, anything beyond a loose connector will probably mean a hot-air station and a good magnifier/microscope at the least. Modern SMD electronics just isn't particularly easy to work on.

I could replace the screen and I could buy a new laptop but I am irritated by those options.

I did some quick research on this, and apparently this problem could be caused by a faulty cable. Or maybe even just a loose cable. The fact that warmth seems to help is a clue that the cable may simply be loose.

Since gaming is important to you, I see nothing wrong with doing that.

If i go ahead with a VM, then I would buy a better monitor that would allow faster refresh than the present external monitor does. I believe/hope that the hdmi output is totally independent of the laptops screen and will provide a better performance for games. It will also be bigger than the laptop screen so that would be an incidental improvement.

The laptop screen seems to start working if it has been been on for long enough - presumably warmth helps - but it is likely to go bad again at any point.

but the start-up reset sets up 144Hz

Does the BIOS have an option to default to 60Hz? If not and not needed, is there an option to disable 144Hz?

I could replace the screen and I could buy a new laptop but I am irritated by those options.

Another solution is to boot straight into an OS - avoiding the need for a GRUB screen but making it hard to choose which OS to run. Does a VM help here?

I could fairly readily have a stable Excalibur as the host system and run  a VM running another Excalibur for experimentation. Ideally, I would like to use the existing experimental Excalibur partition as a source but understand that may not be easy or wise.

I could run Windows within the VM - but is that a good way to play speedy games? Does the double layer of OSs work and I fear that Fortnite does not like VMs.
Again, I would prefer to use the existing Windows partition as the source for the VM rather than have to setup something fresh - but that does not appear to be the standard thing to do.

I could run Windows as the host and run however many Excaliburs in VMs. But I think that is a retrograde step.

I am looking for advice from anybody who has experience of running Fortnite (or games) in VM, or who has VM experinece and can comment on speeds, and setup problems before I launch into this.

Any takers?