If you want to dual-boot Windows and Linux, I strongly recommend that you install them on separate devices, and physically disconnect your Linux device. It's a pain in the ass, but Windows Update has a particular appetite for bootloaders and will eventually eat whatever you have on your EFI partition (including the Linux kernel and ramdisk) and replace it with its own.

Otherwise, you can use Chris Titus' winutil script to delay or completely disable updates, and also to debloat the system and disable anti-features like telemetry and the start menu search.

Not sure if this applies to LTSC, but if you can, install a European edition of Windows (-N suffix) and set an EU location and timezone, it will allow you to more easily uninstall components because of EU regulations.

What is the game? If the company hates you so much to do this, you probably shouldn't support them.

Friends don't let friends play windows.

LTSC is fine, and you can just use massgrave.dev to activate it.

If you want to install Windows on another drive and quite rightly don't want to pay MS for the privilege, then massgrave is your friend.

Put the installer on a USB, remove your Linux drive (because you should install it on a separate drive, and Microsoft will infect your boot partition otherwise), and run it. That’s it.

Then follow the instructions on massgrave to activate it.

Look inside yourself and ask if you really like to play this game that much. Maybe wait a for more weeks and see if your feeling stays the same.

In my experience I can say that these kinds of urges pass away after a while.

If you dual boot, install on a separate dedicated drive of possible.

Saves a lot of headache with windows boot part, especially since you're installing after already having Linux installed.

the safest fastest but expensive way, get a second drive that's big enough to run windows and your game. disable the drive from BIOS boot options and add an entry to your bootloader. i salvaged an old 512gb sata to do this for firmware/some legal document things that only work on Windows.

there's vfio but i believe you still need two video cards to get that working, one for the host one for the vm.

just never trust windows on your main boot drive that only leads to you having to recover your bootloader when a windows update replaces it. and this is not a question of if they will it is a question of when.

If you must run Windows, do it on a completely separate device if you can. That way your one game that's DRM-locked to Windows can stay on its own machine without Windows getting hostile to your Linux install like in a dual-boot.

If you don't have/can't obtain a separate device for installing Windows on and you must dual-boot, the safest way to do that is to disconnect your Linux drive(s), install Windows on its own fresh drive so it can have its own boot partition and its own bootloader, reconnect your Linux drive(s) after your Windows drive is finished setting up and set your EFI boot order to point to your Linux drive, and then set your Linux bootloader, usually GRUB, to query your Windows drive and let you pick it to boot from, that way hopefully Windows stays on its own drive and its own boot partition and doesn't try to screw over your Linux drive and its boot partition.

You can do one of three, for different levels of ease and performance:

1. Install boxes/gnome-boxes, install the windows os on a virtual machine. Just press the plus to choose an iso file and go.
2. If you have an extra hard drive, you can install windows on that hard drive, and have to set up grub to recognise it.
3. Change the partition size of your hd using a live cd/usb version of Linux (you can't change partition size on partitions that are in use) , make a new partition and install windows on that partition. Add this new OS to grub.

You will need to do further research on some of the stuff I said, but I gave you the correct things to look up.

They go down in order of difficulty. Boxes will be less efficient but easiest. The other two have the same efficiency, but the second is a bit more challenging

I have a windows install on a USB hard-drive. It's not fast but that might not be a problem if you use a fast USB storage. I just plug it in and boot from it via UEFI.

Maybe what you want to hear, but I once bought Marathon because it wasn't declared that GNU/Linux is blocked again, like Destiny 2 was. I requested a refund on Steam and 30 minutes later was granted. It's not worth the hassle for one game, IMO.

I used to dualboot for the same situation, just exam software instead of game. You can find entire video tutorials online for dualbooting.

I recently did this, using a VM with GPU passthrough. This meant my Linux OS couldn't use the GPU while it was active. It's a pain in the ass, but it technically works. I won't describe how to do it, because there are good guides online.

I am not an expert on Windows game rootkits (or Windows in general...), but would it perhaps run in a VM?
At least then you wouldn't have to do a "real" install...

Kinda hijacking, pardon me, but is there anyone reading who'd be willing to explain the specifics of "Microsoft eats boot sectors" or direct me to some documents?

I have a laptop with Microsoft / Linux partitioned on a single internal drive dual booting between them and have never... well never known that I had such an issue, but I've broken it in a lot of creative ways, and maybe this Microsoft greedy boot behavior would inform some of it and help me make it smoother

Ugh, I feel you on this. Can't help unfortunately because I just bit the bullet and dual boot, there's just one or two games that don't work well for me on Linux. Best of luck