That part of that answer is wrong.
LTS is based (mostly) on debian-testing
From https://wiki.ubuntu.com/LTS:
- We are more conservative in our package merge with Debian, auto-synching with Debian testing, instead of Debian unstable.
- [LTS is not] Cutting Edge: Instead of doing an automatic full package import from Debian unstable, we will do it from Debian testing. The benefit we gain from not introducing new bugs and/or regressions outweighs the new features and/or fixes we often get from unstable.
- We reserve the right to selectively pull in updates from unstable, if we believe the stability of the package in Debian is better than what is in the current Ubuntu archive.
The obvious corollary is that non-LTS releases are based, for the most part, on Debian unstable.
You can find the Debian version on which your Ubuntu version is based in the file: /etc/debian_version
From 10.04 up to 21.04:
Ubuntu Debian
21.04 hirsute bullseye/ sid - 11
20.10 groovy bullseye/ sid
20.04 focal bullseye/ sid
19.10 eoan buster / sid - 10
19.04 disco buster / sid
18.10 cosmic buster / sid
18.04 bionic buster / sid
17.10 artful stretch / sid - 9
17.04 zesty stretch / sid
16.10 yakkety stretch / sid
16.04 xenial stretch / sid
15.10 wily jessie / sid - 8
15.04 vivid jessie / sid
14.10 utopic jessie / sid
14.04 trusty jessie / sid
13.10 saucy wheezy / sid - 7
13.04 raring wheezy / sid
12.10 quantal wheezy / sid
12.04 precise wheezy / sid
11.10 oneiric wheezy / sid
11.04 natty squeeze / sid - 6
10.10 maverick squeeze / sid
10.04 lucid squeeze / sid
sid is the development distribution of Debian (sid - testing - stable)
You can find out the contents of the file without installing an entire system by view the sources for the package basefiles on Launchpad.
Best Answer
Both.
In every Ubuntu release, there's an initial import from Debian unstable for many packages in
main. After 9 weeks or so, that process is frozen and the versions are locked down.However, there is still tracking done by the MOTU team for universe. Many packages come across from testing. (Many packages are also wholly original too.)
For both sets of packages, bug tracking is done on Launchpad and custom patches will be introduced or backported from the previous Ubuntu release.