I recently bought a System76 Oryx Pro 9, and I could not for the life of me get Debian to boot from a USB. The same USB booted on my old Galago Pro, so I know it was good. The Oryx Pro runs on some FOSS UEFI or BIOS made by System76 themselves, and it doesn't play nice with anything but Ubuntu and Pop!_OS.
I filed a support ticket asking for help, and they told me they only support Ubuntu and Pop. On one hand, I understand having service desk limits, but their garbage UEFI and lack of support left me no choice but to return the laptop. In fact, I thought this article was going to be about people returning laptops to System76!
I really hope they get their game together and make a pre-boot system that can handle non-Ububtu stuff easily. The previous System76 I had was able to handle a Debian install just fine.