It's definitely possible to configure this... it's just not a default on any distro I'm aware of. Linux Full Disk Encryption definitely stops very early and asks for the FDE password before being able to continue booting. After that, you would just have to have your user set to "automatically log in" for it to just go all the way in.

In fact, I think you could choose to set it up this way from the Ubuntu installer directly. By default, it just encourages you to sign in manually in addition to setting up FDE.