I am experiencing the same behavior in Xubuntu 18.04 (has been a problem for a while) when using "open with" on the .deb package from Thunar (right mouse menu). If I start gdebi-gtk from the command line and use the "file open" menu option then everything works ok.
I will dig through my logs for more info. This system is a fresh install of 18.04 Gdebi was the 5th package installed after (gnumeric, gppoder, synaptic, vlc). -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to gdebi in Ubuntu. https://bugs.launchpad.net/bugs/1749728 Title: Installing packages fails when launched via Firefox ("open with") Status in gdebi package in Ubuntu: Confirmed Bug description: When launched from Firefox with the "open with" function, GDebi is unable to complete installing the package. The GDebi window does open, but after selecting to "install" the package the window closes and the package is left uninstalled. ProblemType: Bug DistroRelease: Ubuntu 18.04 Package: gdebi 0.9.5.7+nmu2 ProcVersionSignature: Ubuntu 4.13.0-32.35-generic 4.13.13 Uname: Linux 4.13.0-32-generic x86_64 ApportVersion: 2.20.8-0ubuntu10 Architecture: amd64 CurrentDesktop: MATE Date: Thu Feb 15 17:08:31 2018 InstallationDate: Installed on 2018-02-15 (0 days ago) InstallationMedia: Ubuntu-MATE 18.04 LTS "Bionic Beaver" - Alpha amd64 (20180215) PackageArchitecture: all SourcePackage: gdebi UpgradeStatus: No upgrade log present (probably fresh install) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gdebi/+bug/1749728/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : [email protected] Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp

