I’m aware of Debian’s reputation for not having the most up-to-date software in its repository but have just noticed that Thunderbird is on its current version. Which makes me ask:
When does Debian update a package? And how does it decide when to?
I’m particularly interested in when it will make available the upcoming major release of GIMP to 3.0.
These both can be answered in depth at Debian’s releases page, but the short answer is:
Debian developers work in a repo called “unstable” or “sid,” and you can get those packages if you so desire. They will be the most up to date, but also the most likely to introduce breaking changes.
When the devs decide these packages are “stable enough,” (breaking changes are highly unlikely) they get moved into “testing” (the release candidate repo) where users can do QA for the community. Testing is the repo for the next version of debian.
When the release cycle hits the ~1.5 year mark, debian maintainers introduce a series of incremental “freezes,” whereby new versions of packages will slowly stop being accepted into the testing repo. You can see a table that explains each freeze milestone for Trixie (Debian 13) here.
After all the freezes have gone into effect, Debian migrates the current Testing version (currently Trixie, Debian 13) into the new Stable, and downgrades the current stable version to old-stable. Then the cycle begins again
As for upgrades to packages in the stable/old-stable repos: see the other comments here. The gist is that they will not accept any changes other than security patches and minor bug fixes, except for business critical software that cannot just be patched (e.g. firefox).