I have removed them before. Take off the triangular plastic piece, and there are 4 screws. If your car has the door tweeters, those two bolts are are also used for the mirror so take them out. Then there is one more bolt holding it, and IIRC the fourth bolt is an adjustment bolt.
But yeah, just take off the plastic triangle trim piece and unscrew it lol. They weigh around 1-1.5 kg, and the retractable ones weigh a bit more