Newer versions of the Pi5 firmware are available. Please bump dev-embedded/rpi-eeprom-21.0_p1 to rpi-eeprom-21.5_p1. Its a 'daft laddie' copy/rename/manifest version bump. If it wasn't, I couldn't do it :) Tested default/pieeprom-2024-02-16.bin here and it still boots.
Overtaken by bug 947208
*** Bug 947208 has been marked as a duplicate of this bug. ***
... and 26.9_p1 is here too. That works. 27.0_p1 arrived on 22-Jan-25 but I've not tested it yet.
27.0_p1 latest boots on a Pi5.
rpi-eeprom_27.4-1.debian.tar.xz is out now. , Latest boots a Pi5, thats Wed Feb 12 10:51:52 UTC 2025. The install location has moved to /lib/firmware/raspberrypi/bootloader from /usr/lib/firmware/raspberrypi/bootloader, which requires an edit to /etc/conf.d/rpi-eeprom-update to point to the new location. At least, on split-usr it does.