Addendum 2: Of course, it could be BT, but I thought I'd check-in with you guys first before tackling the behemoth; but to be fair once you get to a actual person, I have found they were knowledgeable and helpful. Anyway, as the problem hasn't been reported here, I'll adduce it's some glitch involving BT and close this question; and my life can move on. Thanks for the (tacit) help.

@lenkhulu I'm glad to hear that!

@mrt10001 Success! I tried what you suggested but I had no luck. I tried what the twrp site said and again no luck. I flashed Android v9 and started again. And that worked. Thanks so much for your help, MrT; it got me started!