Mistakes in the Docs: UART on Raspberry Pi 5 Compute Module

We have a Raspberry Pi Compute Module 5 IO Board without a monitor or network connection. How do you see what the system is doing? How to read the Linux and bootloader log? A simple answer is UART. Turns out, UART isn't so simple on the Raspberry Pi 5 and its documentation, datasheet and raspi-config is wrong in a couple of places.