My understanding is that Patreon does not use Google's payment system and isn't subject to a cut of the revenue. This is why the article says "Your prices on the web and the Android app will remain completely unaffected".
At least until 2025 when Google implements the exact same policy change. Every questionable hardware choice Apple does is something Android vendors or Google Play copies within a year.
Remember when Samsung made fun of Apple for removing the headphone jack?
unlike Apple who has managed to dodge scrutiny, Google is being reemed hard by the US courts over multiple antitrust issues. It may happen eventually, but I think the courts doing their jobs will stall such pivots. The last thing they want to do is make their store sound more like a monopoly.
True, but Android at least allows alternative app stores, and there are a few. Obviously it's not as easy as the native store, but if enough developers are dissatisfied, there is a way out.
You can sideload, but the duopoly exists and they're shaking 99.9% of users down for every dime they can get out of them.