(Abstract)
Far Cry 6 game always says meaning like "Windows version you using, is older than v2004" at main screen, but it's odd because my actual environment is v21H1 of Windows 11. Literally every time and it's makes me uneasy.
Note : I'm playing game on Japanese language edition, and my English writing skill is very low (as you can see now), so there's could be differences in terms.
I don't know how the dev team is getting the version of Windows, and Microsoft / Windows dev side (mainly registry value) may display "This is Win10" depending on the information acquisition method. There's something I would like devs to try (or consider) in this regard.

(Prerequisites)
(1) I'm running game on Japanese edition of Windows 11 Pro 21H1 / Far Cry 6 1.5.0, Japanese UI, English audio.
(2) My hardware is potato, but at least meets the minimum requirements, and I have no plans to build a supercomputer just to play games.
(3) Official help page of Far Cry 6 says;
 "Operating System : Windows 10 (20H1 version or newer, 64-bit versions)"
 (from page where titled "System requirements for Far Cry 6")
 (and as far as I know, there is no 32bit version of Win11)
(4) I accidentally installed Win11. I regret very much because the grace period (10 days or around) has already expired and I can't go back to Win10.
(5) Win11 > settings > system > version info says;
エディション (edition) : Windows 11 Pro
バージョン (version) : 21H2
OS ビルド (OS build) : 22000.675
エクスペリエンス - Windows 機能エクスペリエンス パック (windows feature experience pack) : 1000.22000.675.0

(Conjectures)
The old version information remains in the registry of Win11, but I imagine that it is referring to this.
This is because the cobalt branch of Win10 was launched under the name of Win11 just for business strategy reasons. In other words, I think players and devs of UBI have no responsibility, and the direct cause should be attributed to Microsoft.

Now, for anyone of devs, let try the following simple experiment.

As first, run Windows PowerShell on Win11 (not with cmd.exe), and type
> Get-ComputerInfo | Select WindowsProductName, WindowsVersion
Will give you the following results:
> Windows 10 Pro 2009
(Note : This result meets requirement "v2004 or later")

And then next, type
> Get-ComputerInfo | Select OsName, OsDisplayVersion
This way gives the following results in my environment:
> Microsoft Windows 11 Pro 21H2

(Conclusion)
I think this is the information that should be acquired in game.
In any case, if you change the information acquisition method, devs can avoid the result at the beginning (I mean, displaying "Windows should be v2004 or later").
Again, as you can see by just typing Get-ComputerInfo, the registry value still has both information "this is older version of Win10" and "this is latest version of Win11". Of course I don't know why, so ask to Microsoft.

I hope this is helpful as much as possible.
diagraph01_2, Tokyo, Japan

@diagraph01_2

@diagraph01_2 I have the same thing using Windows 10.

@gameguru2018
Thank you for the tip, I'll try to get it. ...... is certainly a solution for now.

The sad part, however, is that the information seems to have been completely useless for the UBI (or engine) development team. It is really "UBI-like", if you can call it that.

@diagraph01_2

I don't receive a response from the person who wrote this.
and It's obvious that he did not read what I wrote.

This is not a solution, it is an incentive. The forum should be used constructively.