All right, flashed BIOS, can still reproduce the problem.
EDIT: Here’s the most recent log: https://0x0.st/85IX.txt
Interestingly enough, the crash seems to be slightly different now.
Jul 27 13:42:34 Naisa-Linux kernel: #PF: error_code(0x0011) - permissions violation
Jul 27 13:42:34 Naisa-Linux kernel: #PF: supervisor instruction fetch in kernel mode
Jul 27 13:42:34 Naisa-Linux kernel: BUG: unable to handle page fault for address: ffffffffc060d5a0
Jul 27 13:42:34 Naisa-Linux kernel: kernel tried to execute NX-protected page - exploit attempt? (uid: 0)