Matthew, thank you for properly identifying the responsible component of Ubuntu 18.04 that prevents Thunderbird and VLC from interoperating. "gnome-software" is more precise.
This is not a Thunderbird, VLC or snapd problem. This is an Ubuntu 18.04 application packaging issue. The problem is that Thunderbird saves a temporary attachment file in /tmp before invoking a helper application to open it. If the helper application associated with the file is VLC, VLC does not have permission to open the file. (In fact, the system /tmp directory is not even in the VLC snap's filesystem name space.) The solution is to build and configuration VLC for this Ubuntu release so that it shares its /tmp directory with the system /tmp directory, i.e. they are one and the same. -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to gnome-software in Ubuntu. https://bugs.launchpad.net/bugs/1897460 Title: VLC Snap Incompatible With Thunderbird Status in gnome-software package in Ubuntu: Incomplete Bug description: When I changed my default video player from Totem to VLC, Thunderbird was no longer able to play an email message video attachment. By default, Ubuntu Software installs the VLC snap package, whose permission scheme prohibits it from accessing the directory where Thunderbird saves the video file to be played (/tmp/mozilla_andy0). VLC reports: Your input can't be opened: VLC is unable to open the MRL 'file:///tmp/mozilla_andy0/[VIDEO FILENAME]'. Check the log for details. To reproduce the bug: 1. Open a Thunderbird message. 2. Single left click on an attached video file handled by VLC. 3. VLC starts and then opens an error dialog with the above "Your input can't be opened" message. ProblemType: Bug DistroRelease: Ubuntu 18.04 Package: thunderbird 1:68.10.0+build1-0ubuntu0.18.04.1 ProcVersionSignature: Ubuntu 4.15.0-1097.107-oem 4.15.18 Uname: Linux 4.15.0-1097-oem x86_64 AddonCompatCheckDisabled: False ApportVersion: 2.20.9-0ubuntu7.17 Architecture: amd64 AudioDevicesInUse: USER PID ACCESS COMMAND /dev/snd/controlC2: andy 3256 F.... pulseaudio /dev/snd/controlC1: andy 3256 F.... pulseaudio /dev/snd/controlC0: andy 3256 F.... pulseaudio BuildID: 20200629235513 Channel: Unavailable CurrentDesktop: ubuntu:GNOME Date: Sun Sep 27 07:25:42 2020 DistributionChannelDescriptor: # This is the distribution channel descriptor for the OEM CDs # For more information see http://wiki.ubuntu.com/DistributionChannelDescriptor canonical-oem-somerville-bionic-amd64-20180608-47+beaver-turtlebay+X59 ForcedLayersAccel: False IfupdownConfig: # interfaces(5) file used by ifup(8) and ifdown(8) auto lo iface lo inet loopback IncompatibleExtensions: English (GB) Language Pack - langpack-en...@thunderbird.mozilla.org Thunderbird (default) - {972ce4c6-7e08-4474-a285-3208198ce6fd} InstallationDate: Installed on 2019-10-28 (334 days ago) InstallationMedia: Ubuntu 18.04 "Bionic" - Build amd64 LIVE Binary 20180608-09:38 IpRoute: default via 10.3.2.1 dev eno1 proto dhcp metric 100 10.3.2.0/24 dev eno1 proto kernel scope link src 10.3.2.3 metric 100 169.254.0.0/16 dev eno1 scope link metric 1000 MostRecentCrashID: bp-9a0bd632-9768-4302-9c91-9f4f60200616 PrefErrors: Unexpected character ',' before close parenthesis @ /usr/lib/thunderbird/omni.ja:greprefs.js:1141 PrefSources: prefs.js ProcEnviron: PATH=(custom, no user) XDG_RUNTIME_DIR=<set> LANG=en_US.UTF-8 SHELL=/bin/bash Profiles: Profile0 (Default) - LastVersion=68.10.0/20200629235513 (In use) RunningIncompatibleAddons: True SourcePackage: thunderbird SubmittedCrashIDs: bp-9a0bd632-9768-4302-9c91-9f4f60200616 bp-914925c7-43d8-44c0-a57a-4af430200101 UpgradeStatus: No upgrade log present (probably fresh install) dmi.bios.date: 02/05/2020 dmi.bios.vendor: Dell Inc. dmi.bios.version: 2.5.0 dmi.board.name: 0Y2K8N dmi.board.vendor: Dell Inc. dmi.board.version: A01 dmi.chassis.type: 3 dmi.chassis.vendor: Dell Inc. dmi.modalias: dmi:bvnDellInc.:bvr2.5.0:bd02/05/2020:svnDellInc.:pnPrecision3630Tower:pvr:rvnDellInc.:rn0Y2K8N:rvrA01:cvnDellInc.:ct3:cvr: dmi.product.family: Precision dmi.product.name: Precision 3630 Tower dmi.sys.vendor: Dell Inc. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gnome-software/+bug/1897460/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp