Ubuntu – Problem installing .deb in Software Install Ubuntu 20.04

20.04debdpkgsoftware installationsoftware-center

I tried to install some .deb files in Ubuntu 20.04 from GitHub and other internet sources, but when I open it with Software Install it gives me this problem (Failed to install file: not supported). The only way for me to install them is to go to the downloaded file and do sudo dpkg -i file.deb.

Can anyone help? I don't know what to do and I don't want to use the terminal every time.

Any help would be appreciated, thanks

EDIT: that's NOT a problem with .deb in Ubuntu, it is a problem with Software install. I can install every .deb through the terminal but not with Software install, and Ubuntu suggests to install .deb with Software install. That's not a dependencies problem or anything similar, that's an issue with installing .deb WITH Software install and I would like to know how I can fix Software installer

Best Answer

The Problem

Ubuntu 20.04 has two 'Software Install' applications, one is gnome-software and the other is snap-store, installed by Canonical via snap. This snap app software centre has the problem installing local files from the /tmp directory. Can be easily verified by running these commands:

gnome-software --local-filename '/tmp/mozilla_user0/app_amd64.deb' 

snap-store --local-filename '/tmp/mozilla_user0/app_amd64.deb'

The snap-store command will error with Failed to install file: not supported

Workarounds

You can install gdebi or similar software as suggested in other answers but there is a workaround to modify the file association to use the other Software Install which is associated with gnome-software:

Firefox

When choosing application to open change for the suggested or default Software Install to the other further down the list. This second one is the gnome-software association.

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You can verify that it is gnome-software in Preferences->Applications:

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Nautilus

The same can be done within Nautilus by right-clicking and opening Properties for a /tmp/.deb file and switching the Open with from current default Software Install to the other suggestion.

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