Thanks @Wolfgang_S
It worked w/o glitches.
openhabian@openhabHost:~ $ sudo rpi-eeprom-update
BOOTLOADER: up to date
CURRENT: Tue 25 Jan 14:30:41 UTC 2022 (1643121041)
LATEST: Tue 25 Jan 14:30:41 UTC 2022 (1643121041)
RELEASE: default (/lib/firmware/raspberrypi/bootloader/default)
Use raspi-config to change the release.