I found a sort of work around... If you go Krita>Preferences>Canvas Input Settings,
then go to Pan Canvas category, you can delete the option for middle click = pan.
Then go to the Tool Invocation and make a new setting for middle mouse button = activate, it sort of works...
However astrodpad seems to think that once you click, you never release the click (touching the apple pencil to the screen then lifting it doesn't unclick, I don't know how to describe it better haha) so you end up getting straight lines jumping around where ever you touch the canvas next.
I haven't been able to get past this, which is a shame cause the pen pressure seems to register well ): I was hoping this would work since FireAlpaca wont register pen pressure via astropad.