I do have the same problem. No idea what triggered it, all I know is that since installing 5.5.1 the editor appears as background process only. Re-installing, rebooting, nothing helps.
Task manager looks the same as depicted in the post above; however, lauching the editor not only launches UnrealEditor in the background; in Task Manager also a process “Hub for UE5 runtime traces (…) and tools like Unreal Insights” appears.
Any ideas?