I have a fresh install of windows 11 and Epic Games Launcher is the only software showing this issue. All links in the side bar or anything related to account management are opening in Edge Browser as well as every external link on game store pages, instead of my Default Firefox. I have been troubleshooting for about a week as to why only Epic is having this problem.
It is worth noting this previously worked correctly for me but I dont know exactly when it changed, I only noticed it after reinstalling.
I was very hopeful and followed @enpel instructions to the proposed solution but it did not work for me in the end and all behavior stayed the same even after the registry changes mentioned. I am hoping we can bring more attention to this issue in the near future.