Quick technical post because it doesn’t happen that often that I’m that excited for a new feature available in the Pis firmware code (last time was the HTTP boot method 
).
It will soon be possible to update the firmware, stored in an EEPROM chip on a Pi5, in a fail-safe way. Announcement post can be found here. Previously those updates could be a bit risky as a sudden power loss might render a device unbootable. This can be repaired quite easily but required manual work on the device itself.
The Pi5 EEPROM has 2MB of on-device storage (up from 512KB on the Pi4). This is now split into three relevant parts: A 64KB readonly section storing the (I assume) static code that switches between version. Followed by two 988KB sized sections logically named A or B. The code in the readonly section decides which of those it should boot.
Assuming the device booted using version A, the section B is unused. Using a new rpi-eeprom-ab tool that communicates with the Pi’s firmware over mailbox calls, a new version of the EEPROM can be flashed to B. Once that’s done, a reboot with the tryboot flag, should, from what I understand, cause the EEPROM to use the new code in section B.
Importantly: Should this reboot fail for any reason, a watchdog can automatically reboot the Pi after a set duration. Such a reboot will clear the tryboot flag and the previously used version in A will be active again. Effectively such a failure will roll back the system to a previously known working state.
Assuming the reboot worked properly, the running operating system can again use rpi-eeprom-ab to commit the now known good version in B. Any followup reboot will now automatically use B and the next update can repeat the same process with A/B reversed.
The layout in the EEPROM’s binary files (those available here) has slightly changed as certain offsets within that file now carry special meaning. But I’ve already updated the eeprom.py tool info-beamer OS uses and it should support reading and modifying EEPROM images. You can find the updated source at GitHub - info-beamer/rpi-eeprom-tools: Tools for working with the Pi4/Pi5 EEPROM firmware files.
Once this feature is officially released, the EEPROM update process in info-beamer will very likely use those features. It’s still unclear (although I feel unlikely) if this method will also be available for the Pi4.