I support, the launch of the game is already quite long, but here you still have to wait for the mastery window to load. This is useless, especially when all the tests have already been completed.
Even worse when your keyboard and mouse stops responding, as happened when I attempted to play last night.
This happens, especially when managing long rolling stock, but I doubt that this can be attributed to the problem in this topic.
I seem to remember back in the days of TSW2020, when Mastery first appeared, that by disconnecting my machine from the internet, I wasn't bothered by it. The only time I go online now is to download something. Which is probably the exact opposite of what they intended.
Currently the only way to do it is to log out of Dovetail Live. As I am assuming that is the last thing Mastery is supposed to achieve it would be in their own interest to allow players to disable the automatic appearance of it. I thought they would have learnt that from last time. Permanently logging out of Dovetail Live was my greatest achievement in TSW2020 after Mastery drove me to it. It made me so happy. The pop-up was taunting me as Mastery never worked anyway.
I have zero interest in Mastery so the pop-up is particularly annoying. I suppose I could opt out of Dovetail Live, as you suggest.