Thanks, as I said, I tried all the f-buttons already, multiple times, with no success. F10 seems to be the one, but it didn’t work on multiple tries. I’m heading to the office later today where I have different keyboards and displays to try it with.
Another thing I just found on a reddit post was that the USB stick should be no larger than 4GB. Even if that didn’t cause this problem, I’ll get a small USB stick on the way as well, just in case.