A note for future me. Installing the latest wsjt-x on the latest Ubuntu fails. (The version in the software catalog is very old). Here's the tricks. The main issue is that the wsjt-x deb is built against libreadline6 which is no longer available. libreadline7 is there but you need to tell dpkg to ignore the request for 6.
Download wsjtx_1.9.1_amd64.deb from https://physics.princeton.edu/pulsar/k1jt/wsjtx.html
If you previously tried to install wsjtx from the deb file you'll need to tidy up with:
sudo apt --fix-broken install
sudo apt install libqt5multimedia5-plugins libgfortran3 libqt5multimedia5 libqt5serialport5
sudo dpkg --ignore-depends=libreadline6 -i wsjtx_1.9.1_amd64.deb
Update: There's instructions on how to install libreadline6 on linuxer.eu here.