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.
Gimp 3 is scheduled to be released in May, around the time that Debian 13 is about to come out. Given that Gimp is never on time, and that Debian will only include stable software in their repo, you won't see Gimp 3.x on Debian for another 2.5 years (the next major release).
However, don't fret. There's a way to run Gimp 3, even now, without overwriting the 2.10.x version of Gimp that comes with Debian: https://github.com/ivan-hc/GIMP-appimage/releases That's how I run gimp 3 on my Debian too, I just download the 3.0-rc1 .appimage file, make it executable, and it's up and running.
Flatpack is one of the official ways to install the RC:
If you have Flatpack on your system, go to https://www.gimp.org/downloads/devel/ and click the GNU/Linux option, there will be a button to install it.
If the button doesn’t work, the page says:
Flatpak additional instructions
If the link above doesn't open your software installer, install with following command:
flatpak install --user https://flathub.org/beta-repo/appstream/org.gimp.GIMP.flatpakref
Run with following command line:
flatpak run org.gimp.GIMP//beta
To update:
flatpak update
Note: If you installed both the stable and beta repositories, the desktop (menus, etc.) will see only one version at a time. To make sure your desktop sees the development version, run this command:
flatpak make-current --user org.gimp.GIMP beta
Or respectively to restore the stable version as the visible GIMP application:
flatpak make-current --user org.gimp.GIMP stable
You may also create shortcuts running specifically one of the other version.
I don't like flatpaks. Some builds don't support printing, for example. Same for snaps. That's why I always prefer appimage from these types of binaries, but my favorite always remains the repo versions.
Don't use AppImages.