On Monday, 23 November 2020 at 20:24:41 UTC, Ian Jackson wrote:

So can anyone confirm that I have my facts right. Am I safe to buy a
Ring Doorbell 2 and a Chime, and will later be able to add an external
power feed?

I have recently bought the "All-new Ring (2nd generation)", which is NOT the same as the Ring 2, and an "All-new Ring Chime".

Yes, the doorbell is battery-powered. Yes, you can add an external power feed later, which trickle-charges the battery. This is what I have done. It works well.