After some debugging in an PS3 emulator, found some more bugs.
Now it seems to be unable to start up once the UniPCemu base (it's startup is finished) is up-and-running. Somehow I think that the multithreading is running out of memory somehow? Terminating the app seems to work properly (I see it displaying the teardown of the app). So it's probably waiting on the BIOS thread to be able to start during first boot (but can't due to lack of free memory I think?).
But looking at the main thread reveals that it's running the main emulation somehow, although oddly enough the Settings menu (thread) it's supposed to run at the start never starts?
And because it never starts, the input mode is never changed to be properly functioning, as that's the task by the 'BIOS' initialization function (depending on the execution mode etc.). If it functions properly at all that is (the SDL 1.2 documentation of it says that it's unfinished?).
Since the main thread is running (responding to SDL events), emulator shutdown can properly occur though, so terminating the application works as intended.
And there's another weird issue: files can be createn, but not written for some weird reason? The file it created in my emulation testcase is an empty one (and locked while the emulation is still running for some weird reason?).