Followup question: In the Radxa Rock5B Debian image, is the M.2 E 22x30mm slot be configured to PCI mode by default, or must I run some system command to make the PCI work?
I plugged in such an M.2 card now and it is not detected by Linux.
Edit: Made a separate thread for this question: How make Rock5B's 22x30mm M.2 PCIe slot work on Linux?