Overview
Neither Steam or Ubi will fix this, they both doesn´t care about so… here is a quick solution
Easy Fix
It´s quite simple: Go to the install location of the game standard is: Program Files (x86)Steamsteamappscommon
And delete this 3 files inside the Test Server folder:
RainbowSix.exe
RainbowSix_BE.exe
steam_api64.dll
Than go to your Steam library rightklick – uninstall
Done ^^
Greeds BestNoob
(Checkout my Profile there more Guides and cool Workshop Stuff)