What file do you tell the launcher to launch? Maybe that’s the issue? If it’s the same file I mentioned with no extra parameters or anything, I have no idea.
Maybe it’s related to the command-line window that pops up on manually launching it (first line: [Begin Manager Boot])? Seems to initialize the SDL bits. Is it possible to intentionally run it without any of that CLI stuff, as the itch launcher seems to do, and would the same thing happen?