Super vs. GT

So I watched Dragon Ball, then went to Z, then was told that DBKai is just a sped up version of Z and that GT was all filler. So I skipped it and went straight to super. Then I watched the Broly Movie. Then I watched the Super Hero movie. Then I read the rest of the manga.

On Instagram I seen someone claiming that super is filler and GT is canon. I tried to correct him and was met with many people saying I was wrong and now I’m confused. How can GT be canon if Daima is canon don’t they happen at the same time?

TLDR: Is there some secret society of people who believe Dragonball GT is canon and that’s where Dragonball stops?