There is a separate thunderbird app from k-9 now, so apparently not just an update. Obnoxious though that the new app lists a bunch of collected data types while k-9 doesn't list any. Maybe just a legacy thing since K-9 has been around forever and they didn't list them originally, but still upsetting for the privacy minded.
Not gonna lie, I was super confused why F-Droid was updating thunderbird beta on my device when I was updating apps a few days ago. Took me a while to realize k9 was apparently changed to thunderbird beta.
According to someone else who replied to my comment, it seems it's some sort of metadata issue rather than an actual rebrand. I'm just an idiot who doesn't actually look deep enough into this kinda stuff.
Does TB no longer partner with gandi or Mailfence? It used to be that when you did a new install of TB, it would provide links on how to get a new email address with one or both of them. Since TB Android looks to be basically just K9 Mail (?), I'm assuming there's no calendar or calendar sync function?