I know this probably isn’t what you want to hear, but imho without knowing in detail all the changes you tried to make and the fixes you wanted to apply, the most effective method to fix these issues might be doing a full reinstall and starting again.
Even nuking the system won’t guarantee that I don’t have the same issue with the mouse cursor and the onboad graphics display while using Mesa drivers.
I’d rather simply get the DP-VGA adapter in a future and then try with Mesa.
I know this probably isn’t what you want to hear, but imho without knowing in detail all the changes you tried to make and the fixes you wanted to apply, the most effective method to fix these issues might be doing a full reinstall and starting again.
Even nuking the system won’t guarantee that I don’t have the same issue with the mouse cursor and the onboad graphics display while using Mesa drivers.
I’d rather simply get the DP-VGA adapter in a future and then try with Mesa.