I've seen this with Qt Creator's code itself. It gets stuck into loading a plugin and has no way to get further.
My solution was to just start the application normally and then attach to the process.
This worked fine for me, since I didn't need a breakpoint at startup.
In the application output there is the Debug button, so you don't have to hunt down the process in the process list:
Screenshot 2024-03-19 at 11.54.31.png