Comment 4 for bug 2009283

I also found this:

To use a serial port as console you need to compile the support into your kernel - by default it is not compiled in. For PC style serial ports it’s the config option next to menu option:

Character devices ‣ Serial drivers ‣ 8250/16550 and compatible serial support ‣ Console on 8250/16550 and compatible serial port

You must compile serial support into the kernel and not as a module.

at https://www.kernel.org/doc/html/latest/admin-guide/serial-console.html