Not exactly what you’re asking for, but I’ll share what I do. I’m using SaltStack to do config management and one of my salt states brings all packages up to date. This is done every 24 hours. I’m not suggesting you install SaltStack just for that but rather pointing out for people who use config management tools that those might be able to handle unattended upgrades.
On a related note, FOSS suffers from massive positive externality market failure. As a result we underinvest in it.