It’s not a new feature, it’s convenient and also has use cases outside of convenience (it’s also generally going to make stronger keys than any passphrase). Here is one way that has existed for years, except Ubuntu specifically patches it out: www.freedesktop.org/…/systemd-cryptenroll.html
It’s not a lot of work, it’s one command and a one word update in the crypttab.
Secure boot is generally a requirement to use the TPM.