On first launch, prior to using or favoriting any trainers, I was able to create and reproduce a very minor UI error.
Hover over the Quick Games list, and go down to Bloons TD 6 (one of the games already listed on the Quick Game List by default), and favorite the game.
The UI will get stuck at a black screen until the list is moved via scroll wheel or scroll bar.
This does not have any impact on reaching the games list as the error disappears as soon as the list position changes.
Happy to provide log files or a video of the process if needed.