You can avoid airlines that have the 737 MAX in their fleet (domestically, the biggest are United, Southwest and American). Whenever I fly I fly Delta, and I’ll never fly on a MAX because Delta doesn’t have any.

Some airlines do! Qatar and Emirates, I think.

but they rotate them quite a lot, don’t they?

i booked a boeing 787 dreamliner but ended up in a crummy 777 from a decade ago.

Delta showed me when buying online. Let me select seats too.

You can find that at https://flightaware.com just from the flight number...

It should be there among the flight itinerary data, often hidden behind an accordion or tooltip.