I also experimented with an AVAudioSinkNode in case it was only a tap limitation, but same result: anything that relies on audio from the Mac, either through iOS/iPad simulator or directly running as "Designed for iPad" or built with Catalyst, forces the frame count to 512 samples, whether I request smaller or larger.

I am experiencing the same problem after having installed a production binary of the app. When trying to launch the app from Xcode for debugging with the designed for iPad scheme, there seems to be some confusion between the two. If the app is installed, then that's the one that is launched and attached to the debugger (and thus unusable for debugging as it is not the correct build), if the app is uninstalled manually, then Xcode gives the attach failed error. Turning off Debug Executable in the scheme allows attaching, but it seems the version of the app running is not the one built last by Xcode, but the production version installed (even after I uninstalled it!). Where is this cached and how can I clear it completely?