While referencing this answer on how Ubuntu and Debian releases align I noticed that the corresponding Debian releases are happening a year after Ubuntu has already released their LTS based on that particular version of Debian. How does it make sense to release an OS focused on stability when the OS you're building on top of us doesn't even feel it is worthy of actually releasing? Do a lot of bugs get fixed in the first year of an Ubuntu LTS because of fixes bubbling up from the Debian community?
I noticed that the corresponding Debian releases are happening a year after Ubuntu has already released their LTS based on that particular version of Debian.
That is not really a correct assessment. You would need to look at the actual package names and version numbers and not as a whole system. In some parts Ubuntu is ahead at some given moment and in others it is Debian.
There is roughly a 6 months gap between the "unstable Debian" and "stable Ubuntu".
Unstable Debian -> Unstable Ubuntu -> testing, fixing, and feedback to Debian -> beta release Ubuntu -> final Ubuntu release.
Do a lot of bugs get fixed in the first year of an Ubuntu LTS because of fixes bubbling up from the Debian community?
Between the beta and final release you will see more bugs getting fixed. And after the release you often see some extra updates but a lot less than before the final release. And the updates after that also get less and less. Just before the next releases you will also see a bit of an increase in updates (we already got 3 this week :) )
This sort of question pops up several times each year.
And it usually occurs because the term "stable" can have more than one meaning.
LTS releases are stable in the sense that "the software does not change". Enterprise customers found that new releases of Ubuntu with up-to-date software included changes and new features...but tended to create headaches by breaking their established workflows. LTS releases were originally intended to address this issue by promising to not change the software beyond High/Critical bugfixes and security patches.
- Example: Ubuntu 18.04 LTS shipped with Gnome 3.28. It still runs Gnome 3.28, no matter how many upgrades you install, though Gnome recently released 3.40.
- There are a couple exceptions to the-software-does-not-change. Example: Firefox, which has a large attack surface, is updated to the latest version in all supported releases of Ubuntu.
LTS releases are NOT stable in the sense that "there are no bugs". The Ubuntu Developers work very hard to ensure that there are no release-critical bugs (which also happens to be similar to the Debian standard for a new release). There is often a lengthy set of Release Notes detailing issues that were discovered during testing. And, yes, there are indeed a lot of bugfixes, especially during the first year after an LTS release...but most of those bugs are discovered after release. (LTS releases have a LOT of users)
Example: weekly Desktop Team Update. Take a look at how much effort the engineers are putting into coordinating bugs, fixes, and plans with upstream projects...including Debian. These folks work hard to be good citizens of the Open Source ecosystem. Most Canonical Engineers are open-source enthusiasts, and many are Debian Developers too. and this is at the frantic pre-release end of a release cycle; much more upstream coordination will happen in a month at the beginning of the next cycle.
Exception to the calendar cycle: Ubuntu 06.04 was famously delayed two months to 06.06 due to several release-critical bugs. It's the only delayed release in Ubuntu's history.