Now that I finally did the plunge and moved to LineageOS 18.1 (without loss of data, from 17.1, which unfortunately became unsupported the moment 18.1 was out, but I guess that's a reasonable price to pay for the excellent options we get through those alternative ROMs), I thought I'd go the whole way and get root plus SafetyNet out of it, too, thanks to the instructions here. They seemed straightforward enough, and the adb USB connection from my old and trusted Thinkpad had already proven dependable.
And it worked like a charm, too!
I'm not completely happy with the results, though,