Thank you. I initially imported into the default iTunes/Apple Music format, AAC or whatever. It was from a CD. Nothing's protected, nothing's in the cloud, so far as this is concerned.
The 'Create MP3 version' is just greyed out. From reading the instructions all over, it shouldn't be. Yes, of course, I can deep-six this version of the album, and try importing again, having set MP3 as a default. We'll see if that works.
Regardless, according to all the online guidance I see, I should be able to create an MP3 copy from the AAC version I already have. And I can't.