There's way more evil things about Windows, like click to raise and menu bars.
personally, i think XDG_CONFIG_HOME + a robust config file framework with a standardized format (yaml/toml, whatever) would work as well. being able to specify a schema could be extremely useful, too, to prevent borked configs. as you've said, we've seen a lot of tools/OS's go this direction. and it doesn't have to be perfect, the 80% case would be a huge improvement.
i'm also sure the registry made a lot of sense at the time. it was probably way quicker than reading and parsing files. we didn't care so much about sandboxing/isolation and backing up. people probably had less application installed.
As many others I haven't liked vanilla Ubuntu since they swapped Gnome 2 for a (what I think is a) clone of the Mac OS interface, but my desktop still uses the Ubuntu 18.04 base system under the hood so this might come in handy for a number of people like me.
https://people.canonical.com/~ubuntu-security/cve/universe.h...
So, Ubuntu's LTS support is only relevant security-wise if you mostly stick to the main repository.
https://www.debian.org/security/faq#contrib
However most packages in Debian are in main. AFAIK contrib is for FLOSS packages that somehow depend on packages that are not FLOSS.