To install Pulse Secure for Ubuntu 20.04, it is a bit complicated since the support isn't great.
First, we'll want to go through the form at https://www.pulsesecure.net/trynow/client-download/.
You'll get an email with download links to the latest versions of pulse secure. Download the Linux
one with the deb file and then you can install it using dpkg from your downloads folder.
$ cd ~/Downloads
$ sudo dpkg -i ps-pulse-linux-[your-pulse-version]-ubuntu-debian-64-bit-installer.deb