Closing the bug then, thanks. There was a matching dev binary but you hit a special case where the stable update failed verification and was removed and you were left on a version that doesn't exists anymore, that's one of the risk of opt-in for proposed updates.
** Changed in: gtk+3.0 (Ubuntu) Status: Incomplete => Invalid -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to gtk+3.0 in Ubuntu. https://bugs.launchpad.net/bugs/1915092 Title: lib-gtk-3 / lib-gtk-3-dev NOT compatible Status in gtk+3.0 package in Ubuntu: Invalid Bug description: I'm using Ubuntu-Mate 20.04 and I am trying to compile California (a calendar program) which requires libgtk-3-dev. When I try to install libgtk-3-dev I get: The following packages have unmet dependencies: libgtk-3-dev : Depends: libgtk-3-0 (= 3.24.23-1ubuntu1) but 3.24.23-1ubuntu1.1 is to be installed So I look at what versions of libgtk-3-0 are available 3.24.23-1ubuntu1 and 3.24.23-1ubuntu1.1, of which the latter is installed. So I tried to force install the older version so that it would be compatible with the dev files but it then tries to uninstall my entire Mate desktop, NOT ACCEPTABLE. Launchpad says NOT to self compile Gtk-3 because it's already installed in Ubuntu 20.04 but the version installed seems to be borked having not been compatible with the development packages making it impossible to compile anything that uses gtk-3. ProblemType: Bug DistroRelease: Ubuntu 20.10 Package: libgtk-3-dev (not installed) Uname: Linux 5.11.0-rc7 x86_64 ApportVersion: 2.20.11-0ubuntu50.5 Architecture: amd64 CasperMD5CheckResult: skip CurrentDesktop: MATE Date: Mon Feb 8 16:45:13 2021 InstallationDate: Installed on 2020-08-10 (182 days ago) InstallationMedia: Ubuntu-MATE 20.04.1 LTS "Focal Fossa" - Release amd64 (20200731) SourcePackage: gtk+3.0 UpgradeStatus: No upgrade log present (probably fresh install) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gtk+3.0/+bug/1915092/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp