https://arstechnica.com/gadgets/2021/02/ubuntu-core-20-adds-secure-boot-with-hardware-backed-encryption/

Canonical released Ubuntu Core 20 today, and it is now available for download. If you're already familiar with Ubuntu Core 20, the standout new feature is added device security with secure boot, full-disk encryption, and secure device recovery baked in. If you're not familiar with Ubuntu Core yet... read on!

The key difference between regular Ubuntu and Ubuntu Core is the underlying architecture of the system. Traditional Linux distributions rely mostly on traditional package systems—deb, in Ubuntu's case—while Ubuntu Core relies almost entirely on Canonical's relatively new snap package format.