I think I have the same problem on Fedora 42 KDE with BlueZ version 5.83-2, and I’ve already tested version bluez-5.84-2.fc42.x86_64 (I downloaded it from https://koji.fedoraproject.org/koji/buildinfo?buildID=2830612), but I’m still experiencing the same issue. I was able to solve it by downgrading to version 5.80 (the only previous one that worked correctly and is available in the repositories), but I opened the following reports:
BlueZ GitHub Issue:
https://github.com/bluez/bluez/issues/1570
Fedora Discussion Thread:
https://discussion.fedoraproject.org/t/bluetooth-a2dp-regression-in-bluez-5-83-5-84-connection-fails-on-startup-tp-link-ub500-plus/165055
Fedora Bugzilla Entry:
https://bugzilla.redhat.com/show_bug.cgi?id=2397966