FYI you also can't roll your own hub support because the current SDK does not let you open an endpoint for address 0, which is needed for device enumeration. I got things working up until that point and then was stuck.

No and in fact the flash is loaded with garbage. If you try to boot it, it will repeatedly output "invalid header" messages.

I don't think you can call uart_write_bytes from an ISR.
If that's not it, throw some esp_printf()s around every line and see which one is causing the reboot.

That worked as well.

What version of ESP-IDF is that in?

I'm not sure if that Q was meant for me or OP but I am using the latest (as of a few days ago anyway) from the master branch.

I was having this issue with an S3 and Bluetooth in controller only mode as well. Short answer: Set the secondary console output to "No secondary console" in ESP System Settings. It is set to JTAG by default, at least starting from the USB host example. Longer answer: I also traced it down to the sa...

Try running install.bat from the esp-idf folder manually. I was having the same issue when I tried to reinstall it after it had been working fine for a while.