Ubisoft games with UPlay - Activation code pairing

Compatibility Report

• Name of the game with compatibility issues: For example Rayman Legends or SplinterCell BlackList, but probably more.
• Steam AppID of the game: 242550, 235600

System Information

• GPU: Irrelevant
• Kernel version: 5.15.13-arch1-1
• Proton version: Any

I confirm:

• that I haven't found an existing compatibility report for this game.
• that I have checked whether there are updates for my system available.

Symptoms

Ubisoft games with UPlay integration probably contain some king of trigger, which links game bought on Steam with my Ubisoft account. This mechanic does not work in Proton and I am therefore asked for an activation key (in Ubisoft client, which launches the game).

• Steam support automatically discards my ticket as soon as it discovers I am not running Ubuntu, which is IMHO irrelevant in this case.
• I got my issue resolved for Rayman Legends by Ubisoft support.
  • After a week of chatting with their support and by providing them a proof of purchase and various screenshots, they manually linked the game to my Ubisoft account.
  • After that, the game launches without any problems.

Yesterday I bought SplinterCell franchise and Blacklist has the same integration => same issue. Right now, I am chatting with Ubisoft support again, but it needs better resolution. As soon as they figure out I am using Linux with Proton, they are going to discard it as quickly as Steam support.

Easy solution would be to display activation code in Steam, so it would be possible to manually enter it on failure? There used to be an option like this, and there is for some games (I can view my CD key for Unreal Tournament 3 for example), but not for those two which actually need it.

Steps which occurred to me

• Game is installed through Steam without any problems.
• Game is launched for the first time - Ubisoft client is launched and auto-updated, than it does nothing for several minutes.
• Game is stopped using Steam and launched again for second time - Ubisoft client loads up and asks for credentials.
• After logging in, client asks for activation code
  • Which I don't have, it is somewhere in steam and is not accessible by me.
  • For Rayman Legends, there is a DLC called Game key, but no key is displayable.
  • Ubisoft client wont let me play the game until I activate it.

No source file, test, or entry point is named. Start by reproducing the Ubisoft activation flow with Steam AppIDs 242550 and 235600 and compare the first and subsequent launches; done would require a defined, working way for the games to obtain or accept their activation credentials.