[18:05] <alram> Hi there! So ... I just had some issues with my Xubuntu (21.04) running from an SSD on the RPi4B; here's a brief description https://paste.ubuntu.com/p/SXnzTTsNtS/
[18:06] <alram> This happened just today, on another endpoint running Xubuntu on RPi4B the same way, I noticed that the 'ubuntu-advantage-tools' apt package would neither install properly nor uninstall properly. 
[18:06] <alram> (I have 'hirsute-proposed' stuff enabled on apt updates, so ...) 
[18:09] <alram> aarch64, so it's the 64bit arm version. the rainbow of death comes like 1 second after the bootup sequence finds the attached SSD drive. I've sometimes had this type of issue when there's been an EEPROM mismatch; Ubuntu does their EEPROM stuff their way, and it's been pretty hard to find any proper documentation of just how the whole uboot process works.
[18:10] <alram> What's weird though is that the other endpoint would not find any 'libc-bin' related updates, am just scratching my head on what the problem might be. None of the system logs under /var/log/ show any errors, etc ...