I’m happy to find that calibre worked overnight as I hoped: after a few days of tinkering with setting it up on my little Ubuntu NUC, it’s pulling a couple of news and reading sources into daily digests and sending them to my kindle via email. I wish that kindle were more flexible with ad hoc reading (and it’s one reason I’m thinking about a kobo), but this is a nice, effective step toward how I would like it to work.