Unattended-upgrades is one of the reasons I used to install Ubuntu as a default server OS. Combining that and an automated reboot is practically all you need to keep your server secure enough in most cases.
Ubuntu runs boost 1.74 just like Debian. Upgrading to a new version is likely to break stuff and neither Ubuntu not Debian are rolling release distros, so it wouldn't make sense for them to update already. The upcoming 23.04 not containing the newer Boost version makes less sense, unless there are compatibility problems that can't be fixed before release.
Either way, Debian is Ubuntu without all the Ubuntu. If Ubuntu works for you now, Debian will probably work for you with minimal changes to your workflow. In many cases it packages more recent versions of software because it's "LTS" cycles are faster than Ubuntu's.
If you want rolling release updates completely under your control, consider Arch or one of its derivatives (Endeavour/Manjaro/etc.) instead. All three of them come with the warning that a standard system update can make your OS unbootable if you don't read the change logs, but that's just a consequence of always using the latest and greatest.