Some postinstall script failed when using gdebi for installation. Then using apt this:
sudo apt install --reinstall ./OpenWhispr-1.7.4-linux-amd64.deb
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Note, selecting 'open-whispr' instead of './OpenWhispr-1.7.4-linux-amd64.deb'
0 upgraded, 0 newly installed, 1 reinstalled, 0 to remove and 0 not upgraded.
Need to get 0 B/414 MB of archives.
After this operation, 0 B of additional disk space will be used.
Get:1 /home/roly/Downloads/OpenWhispr-1.7.4-linux-amd64.deb open-whispr amd64 1.7.4 [414 MB]
(Reading database ... 690489 files and directories currently installed.)
Preparing to unpack .../OpenWhispr-1.7.4-linux-amd64.deb ...
Unpacking open-whispr (1.7.4) over (1.7.4) ...
Setting up open-whispr (1.7.4) ...
Processing triggers for desktop-file-utils (0.27-2build1) ...
Processing triggers for hicolor-icon-theme (0.17-2) ...
Processing triggers for gnome-menus (3.36.0-1.1ubuntu3) ...
Processing triggers for mate-menus (1.26.1+mint1) ...
Processing triggers for mailcap (3.70+nmu1ubuntu1) ...
N: Download is performed unsandboxed as root as file '$HOME/Downloads/OpenWhispr-1.7.4-linux-amd64.deb' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied)
Some postinstall script failed when using gdebi for installation. Then using apt this: