Raspberry pi flash utility is considered now as production ready and with it is now really easy to flash eeprom on raspberry pi 3B & 4B. Newer boards come with updated bootloader that allows to boot from USB drive out of the box.
No action required
Newest raspberry pi OS will update eeprom automatically when a fresh version of OS is run form SD card for for the first time. Manual update should be performed on RPi’s that are currently running on old OS version. So it’s good to have an updated OS:
sudo apt get update
sudo apt get upgradeVerify eeprom version
sudo rpi-eeprom-updateShould give
BCM2711 detected
Dedicated VL805 EEPROM detected
BOOTLOADER: up-to-date
CURRENT: Thu 3 Sep 12:11:43 UTC 2020 (1599135103)
LATEST: Thu 3 Sep 12:11:43 UTC 2020 (1599135103)
FW DIR: /lib/firmware/raspberrypi/bootloader/default
VL805: up-to-date
CURRENT: 000138a1
LATEST: 000138a1Flash new eeprom
sudo rpi-eeprom-update -a