archiso does not expose serial console
When installing on a PC Engines machine, I realized, that we do not setup serial console by default for archiso. IMHO this should still be provided, so that true headless systems (only accessible via serial port) can be installed/ accessed as well.
A common way would be to add
console=ttyS0,115200 to the kernel cmdline options. I'm not aware whether we can do this for the bootloader itself as well, but will investigate.
115200 is the baud rate commonly used in old serial modems.