Recently upgraded from F42 to F44. Observed that my daily sudo dnf --refresh upgrade command now queries a new repo: Adoptium. Can’t find much info about this repo other than an association with JDK/Eclipse. This repo sometimes causes dnf to hang.
Is this repo necessary or can it be removed?
I also saw this, and I removed the repo with no negative effect that I can see.
I believe it comes from this ‘adoptium-temurin-java-repository’ package, which seemed to get installed as a weak dependency of a JRE package when I upgraded to F44.
It’s part of this change: Changes/ThirdPartyLegacyJdks - Fedora Project Wiki
Basically allowing users that need older legacy java stacks to easily install them. 
If you aren’t using/developing with older stable java, you don’t need to keep it enabled…