After leaving the Yardbirds, Keith Relf formed Renaissance, in similar mold, before forming Armageddon.
Renaissance, now featuring Annie Haslam on vocals, went the rock-jazz-prog route.
Albums you might want to investigate - “Prologue” and “Ashes Are Burning”.

Captain Beyond, especially the first album, where the songs segue and blend seamlessly.

My brother is a huge fan of Transatlantic. I don’t “get” these guys, but their pedigree is impressive.

At another joint I frequent, members are keen on Hats Off Gentlemen It’s Adequate.
https://www.youtube.com/watch?time_continue=9&v=iOk5OvYQ7zQ

Don’t want to forget Galneryus. Raise My Sword!
https://www.youtube.com/watch?v=prBxPljqt0M

There are some documentaries out there. I’ll queue into the few review thread.