Hi, just to confirm that I've installed the latest alpha version (3.581), and have tried restarting my computer.
The issue is that the default touch bar buttons are now appearing - I've attached an image. As you can see the 'x' close button is appearing on the left, and the 'left arrow' is appearing on the right (which opens the default touch bar controls when pressed). If I press the arrow on the right, and then close the default touch bar controls using the 'x' on the left, BetterTouchTool then becomes hidden completely and I have to unhide it from the menu.
I am running BigSur 11.6, and this was also occurring on 11.4 - on a Macbook Pro 2019
Thanks, if need any other information please let me know!