do LED interior lights have bulbs that can be replaced?

If they are discrete bulbs in a socket, then sure, check online and you can find replacements. But you probably wouldn't be asking if they were socketed bulbs that are easily replaced.

My LED lights have surface mount LED's soldered to a circuit board - those LED's are not (easily) replaceable. But flickering LED's sounds more like a driver problem than a bulb problem -- the constant current driver that powers them is probably going bad.

Probably easiest to just replace the entire fixture.