flatpak fails, seemingly entirely

I have a piece of software that I want to install that's distributed as a "flatpak". However, after installing the flatpak system in my Ubuntu Mate 20.04 system, it fails to load the package I want to use. I get this error:

$ flatpak install chirp-daily-20220103.flatpak 

Note that the directories 

'/var/lib/flatpak/exports/share'
'/home/simon/.local/share/flatpak/exports/share'

are not in the search path set by the XDG_DATA_DIRS environment variable, so
applications installed by Flatpak may not appear on your desktop until the
session is restarted.


** (flatpak install:41527): WARNING **: 20:31:39.113: Error unregistering authentication agent: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name :1.235 was not provided by any .service files
error: Authorization error: Message recipient disconnected from message bus without replying

Further, attempting to list flatpaks doesn't seem to work either, so I don't know what else I can try:

$ flatpak search vlc
No matches found

The above, as best I understand, should list options for installing vlc.

Thanks to all for the efforts to assist. Sadly as of today (Jan 10) there's no improvement. I followed N0rbert's guidance to install / upgrade from the PPA (my original install was directly from the core repos "sudo apt install flatpak"). The installation seemed to work, but on attempting the remote-add, it fails:

$ flatpak remote-add --if-not-exists flathub https://flathub.org/repo/flathub.flatpakrepo

** (flatpak remote-add:37255): WARNING **: 15:10:26.654: Error unregistering authentication agent: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name :1.139 was not provided by any .service files
error: Authorization error: Message recipient disconnected from message bus without replying

Is this possibly a Mint-specific thing? (I guess I'll try it on one of my other machines that has vanilla Ubuntu 20.04.)

Any suggestions?

Solution 1:

Your Flatpak version may be out-of-date. Install newer from official PPA as follows

sudo add-apt-repository ppa:flatpak/stable
sudo apt update
sudo apt install flatpak

then add default FlatHub remote and retry installation of Chirp:

flatpak remote-add --if-not-exists flathub https://flathub.org/repo/flathub.flatpakrepo

cd ~/Downloads
wget -c https://trac.chirp.danplanet.com/chirp_daily/LATEST/chirp-daily-20220103.flatpak
flatpak install chirp-daily-20220103.flatpak

Then reboot to get flatpak registered in system, and finally launch CHIRP from Applications or Brisk menu.