IIUC, the RPi OS that worked well was using the Tue 25 Jan 14:30:41 UTC 2022 (1643121041) firmware.
This is NOT a firmware, it's a bootloader, stored in RPi 4B's EEPROM. Until it's upgraded/downgraded automatically by OS or manually, it stays there even you boot from another microSD card or HDD.
The firmware files are stored on boot media's partition (.elf files etc.). So they are different with every boot media used.
I don't know which firmware version uses latest LE Nightly but you can compare them with files on RPi OS which works for you.