Since version 4.0 the version numbers have nothing to do with changes and are strictly time based. Linux 5.0 happened after Linux 4.20 because Linus “ran out of hands and toes to count on”, same thing with 6.0 after 5.19
Wait. He lost a finger or toe???
Edit: more seriously it’s been since 3.0 after being on 2.6 forever
there are no special landmark features or incompatibilities related to the version number change, it’s simply a way to drop an inconvenient numbering system
It used to only get bumped after a major new feature update, but it was stable enough at 2.6 that it got stuck there for 8 years, so he switched to a different update number