Tbf most devs probably want to do it, they just can't justify it financially. Most games' programmers are computer nerds, and they would be the ones in charge of implementing that kind of stuff. They'd happily do it because obviously, as computer nerds they love Linux, but even if they accept to do some unpaid overtime just because they really want to implement this, it might get blocked by the publisher because they don't want that kind of stuff to bypass QA especially since it has a chance of affecting all users, and when looking at the numbers, it's just not profitable to them.

Now the steam deck could change that dynamic because it has a decent market share, and I would love to see the actual numbers but I'd be willing to bet that most deck owners buy more games than the average player.

Source: am games' programmer, computer nerd, and steam deck owner

Tarkov is in a different much more complex situation. It uses some Battleye addons that are custom made for the game that Battleye will not port to work on Linux.

I think the Steam Deck is a platform that devs are aware of, and I'm sure they don't want to alienate that segment of their sales. They also want to avoid negative reviews.BattlEye is also supported in other games on Linux, including native versions, so it shouldn't be a big deal to ensure its functionality.

This might be a stupid question but is it possible to copy the files you need to your Uplay install? It doesn't guarantee that the game will use them but worth a try I suppose.

Also you have Division 2 on Uplay and Steam? Why?

The Division 2 uses Easy Anti-Cheat (EAC) not BattleEye

This is why client-side anti-cheat is a terrible idea. It gives you the illusion of control, but really it doesn't prevent a motivated party from cheating, and it opens up everyone else to kernel-level vulnerabilities when the anti-cheat software inevitably has a bug.

Client side anti-cheat should merely discourage low effort attacks, and the real cheat detection should always be server side looking at patterns of behavior. Unfortunately, it's a lot easier to reach for client side anti-cheat than build an effective server side anti-cheat.

I'll do my best to explain:

Firstly, not all code executed on an open source OS needs to be open source. For example: Epic Anti-Cheat, which comes with a Linux-compatible mode, is fully closed source. So right off the bat we're going to put to bed the notion that somehow the platform of choice makes it easier for bad actors to pull apart and examine anticheat software.

Secondly, yes, there is a problem with cheaters being able to hide from anticheats on Linux. This is because on Windows it's relatively easy to run kernel-level code via drivers -- this is why most anticheats require admin permission to install a monitoring driver before the game will run. The anticheat is effectively rootkitting your system in order to circumvent other rootkits that may be concealing epic cheatz.

On GNU/Linux, almost all device drivers come prepackaged in the Linux kernel, so there's no direct equivalent to the Windows approach of allowing users to install third-party code into the most protected rings of the OS. It's still possible through the use of kernel modules (see NVIDIA drivers), but as evidenced by how annoying it is to use NVIDIA devices on Linux, this is a huge PITA for both the developer & the user to deal with.

So that's the rub. On Linux, anticheats just have to trust that the kernel isn't lying. This has been a perpetual thorn in the side of developers like Google, who'd really really like it if they could prove beyond a shadow of a doubt that a given Android device is not rooted (see SafetyNet). Google's solution to this has been to introduce hardware-backed attestation -- basically a special hardware chip on the device that can prove that the kernel software has not been tainted in any way.

I am geniunely curious how anti-cheat works on an PC with physical access, where user can plug their mouse loaded with cheats.

For every malware anti-cheat there will be sandboxing cheat.

What I've heard is that they don't think that it's a big enough market to have to fix bugs that might happen only on linux and such, so they just don't allow us to play.

Some require kernel level access, which is a big security risk.

League of Legends does work but it's painful. I use an AUR package called leagueoflegends-git which was the only way I could get it to work on my setup.

https://leagueoflinux.org/ has been invaluable. It used to be a subreddit but it's been made private since the API debacle.