I get it. There are other things I could have done. But like a lot of folks, I tried following the directions for various libraries and failed. I googled a bit and stumbled on this forum (other parts of which I'd used in the past). I didn't read the "how to get the best..." article, because I'd used it before (albeit a different section). And eventually I gave up and found a solution on my own, and thought "this might help someone, so I'll write it down."
Now Jean-Marc is convinced that it's useless, and that's perfectly OK by me. But if I had seen this, it would have saved me a few hours of annoyance.
(By the way, I definitely appreciate Jean-Marc's work on libraries...)
Here, by the way, is a link to the device I bought, even though I think that's completely irrelevant: Lilygo® ttgo t5 wifi wireless module bluetooth base esp-32 esp32 2.13 e-paper display development board Sale - Banggood.com, because the support pointers (and indeed, the name provided for the device) are what misled me into hours of screwing around.