For everyone who will be coming here to install ipfire on their Raspberry Pi 4 rev 1.4 or 1.5 and want to boot it from SD Card:
With latest rpi-eeprom-update Version 138c0 from 11.01.2023 (Updated via Booting from latest Raspberry OS and running “rpi-eeprom-update -a -d”) and ipfire-2.27 core 171 aarch64 ipfire is working when booting from SD card. (core 172 and 173 are Not working with SD Card)
For SD boot to work, the bootimage still has to be rebuilt like stated in this post: Raspberry Pi 4 Model B Rev 1.5 - error -5 whilst initialising SD card - #8 by wiesel
172 and 173 are working, when booting from USB - I will try to find out the difference, why 171 is the last working version for SD card.
Greetings