I am aware of ways to hide it without paying, with adblocker etc.
However, I think if you are a Patron, if it doesn't exist already, there should be an option unlocked under lichess.org/account/preferences/display to HIDE the Donate button.
However, I think if you are a Patron, if it doesn't exist already, there should be an option unlocked under lichess.org/account/preferences/display to HIDE the Donate button.