The idea that we might have a Star Trek series that doesn't generate any books is just plain wrong and does not bear thinking of.
One thing that would be fun to see, but it'll never happen: a Lower Decks novel that treats the show as being as serious as any of the other Trek shows. The occasional bit of character-based humour, but for the most part playing it straight, complete with, say, the real Tawny Newsome in a Starfleet uniform on the cover.
Much more likely: things like the Kirk-Fu book. Boimler's Guide to Getting Ahead in Starfleet, anyone? Tendi's Cerritos Orientation Manual, with her (and the others') handwritten notes over a semi-serious ship guide. Captain Freeman's Guide to Parenting in Starfleet. There's a lot of fun ideas that could work.
A making of/art of Lower Decks coffee table book seems like an obvious choice.
I'd love some proper Lower Decks fiction, too, but sustaining the tone for a full novel might be a bit much. An anthology, as others have suggested, maybe. Or the occasional ebook novella, though they haven't done any of those lately. But we've got to get something.