Can we include bands that changed their sound after they’d become famous? If not, well, please ignore this whole post.
Eurythmics were synth-pop for their first four albums, then switched to Motown-inspired pop rock for two albums, then went back to synth, then went back to rock, then broke up, then got back together and did adult contemporary, then broke up again.
k.d. lang went from country to modern-day torch singer.
Cher started out doing sort of folk-inspired, very sixties-sounding (because it was the sixties) pop, then switched to disco, then switched to what I would describe as an extremely light version of hair metal (basically pop-rock with “darker” imagery), then went to club music, and apparently is about to come back again with a country-rock album.
With her last album Kelis switched from R&B to dance with barely any traces of her previous style.
Nelly Furtado was a sort of neo-soul-folk-world-singer-songwriter-whatever and when that started to fail she came back as an R&B singer produced by Timbaland (to huge success).
No Doubt became famous when they softened up but I don’t know whether that would be a change of genre or more a watering down of their original sound.
Pink’s first album was R&B in the vein of TLC but she quickly changed to her current pop-with-guitars (often described as “pop-rock” but it doesn’t really sound rock-y at all) style.