10 years security updates, plus security patches for community packages (instead of waiting on community patches). It's basically the corporate support plan provided for free for up to 5 machines per account.
Exactly. In Debian, the community implements security patches. In Ubuntu, Canonical implements security patches for a part of the repo (main), the community implements them for the remainder (universe). This has been the standard since Ubuntu's inception. With Ubuntu Pro, Canonical implements security patches for the whole repo (main and universe).
Not necessarily. For all of these cases, Debian, Ubuntu, Pro, the community and Canonical are package maintainers. Implementing patches means means one of: grabbing a patch from upstream and applying it to a package (least work, no upstream contribution); deriving a patch for the package from the latest upstream source (more work, no upstream contribution); creating a fix that doesn't exist upstream and applying it to the package (most work, possible upstream contribution). I don't know what their internal process is for this last case but I imagine they publish fixes. I've definitely seen Canonical upstreaming bug fixes in GNOME, because that's where I have been paying attention to at some point in time. If you consider submitting such patches upstream as actively involved in project development, then they are actively involved. I probably wouldn't consider that active involvement.
Yeah, it's fine. Haven't had too much trouble in a good 10 odd years, once the WiFi drivers settled. Mind you I'm not fucking upgrading to 24.04 for another couple of weeks.
Spent a ton of time trying to install GrapheneOS because web USB doesn't work in snap version of chrome. How about letting me install the normal deb version? Nope, can't let the user choose
Pretty much. Canonical made a few questionable choices in the past but overall they've done a lot for the Linux community. And their distro is very good. There is a reason why distros choose it as their base.