Thunderbird 68.4.1 (64-bit) on Ubuntu 18.04.3 cannot open documents attached to messages.
If I want to open rather than save an attached document, e.g. pdf, ods, I click Open and the result is "no application found for pdf files." If I click View All Apps, the following are listed: Logs, Thunderbird, Thunderbird Mail, URL Handler Script. I know where the apps reside but I don't have the choice to type in the location. If I try to set it up thru Preferences/Attachments, TB goes into my file manager home directory and doesn't allow me to open the directory /usr/bin where the apps reside. I can open /usr/bin directly from the file manager, but not when it is TB that opens file manager. Thus I have no way to tell TB what apps to use to open attachments directly. I can only save the attachment somewhere and then open it from within file manager. The profile I am using in TB came from Win7 OS. There have been some other things that have had to be tweaked in the profile for ubuntu but everything seems to be working fine now except opening attachments directly.
Wšě wotmołwy (5)
If I try to set it up thru Preferences/Attachments, TB goes into my file manager home directory and doesn't allow me to open the directory /usr/bin where the apps reside.
I'm not sure what 'doesn't allow me' means.
To select a helper application you'll have to click through the path to the location of the desired helper application in the 'Select Helper Application' window.
What exactly prevents you to go to a specific path?
You haven't mentioned what desktop environment you use, and not everyone is using Ubuntu. Using Gnome here, and there is a 'Other Locations' button to get to the / directory. From there you can reach any path and location in the file system. Having said that, the 'Select Helper Application' window is a widget provided by the OS, and has got nothing to do with Thunderbird. So you may be better off asking in an Ubuntu forum.
From TB Preferences, an attempt to open /usr/bin results in the following:
https://user-media-prod-cdn.itsre-sumo.mozilla.net/uploads/images/2020-03-07-10-31-48-8d0afb.png
Permission is not denied when I open /usr/bin from Nautilus (file manager). So there is something about accessing from TB that is affected by permissions.
One thing I notice in examining /usr/bin, is that virtually all apps are located there but TB is not. Does the installation program specify the location of the executable? If so, where?
Another user had a similar issue with Firefox, where the setup had multiple drives:
Does the solution fix it for TB?
Unfortunately, no. Turns out this is a permissions problem in ubuntu. TB installed as snap version rather than apt version per feedback from ubuntu support. Reinstall of TB using apt may fix. At this point, I've spent as much time on this issue as I want to spend. I'll just copy to desktop and open there.
Did you ask in an Ubuntu forum?