Download Pass Butler for your Ubuntu/Debian system:
Now you should find Pass Butler in your application menu.
For automatic updates in the future, add Pass Butler repository:
$ echo "deb https://apt.passbutler.de bullseye main" | sudo tee /etc/apt/sources.list.d/passbutler.list
$ wget -q -O - https://apt.passbutler.de/signing-key.gpg | sudo apt-key add -
Now you will get updates of Pass Butler automatically via your package manager.