Same here. I run Xcode 15.2 on Sonoma 14.2, iMac Retina 5K, 27", 2019, 3,6 GHz 8-Core Intel Core i9.
I have a fairly large and old project which I really depend on, but debugging iOS stopped working reliably. I do not see NSLog messages any more (console is visible, of course) and breakpoints get ignored if I do not start the iOS app manually instead of from the scheme. But on the same machine I can debug a new project right from a template fine. I did not find out which project settings could be wrong yet.
I think this started when I installed Xcode 15, coming from Xcode 14.
Did you try to debug a blank new project already?