Download the RPM version from the official website.
Install a dependency:
sudo pacman -S gtk-engine-murrine
Unzip the file: firmador-bccr8.0amd64.rpm
Move the binaries to the expected location. The launcher will look for the files in /opt/Firmador-BCCR/, if the files are not there the launcher will failed
sudo mkdir /opt/Firmador-BCCR/
sudo cp -p -r ~/Downloads/Firmador-BCCR/ /opt/
Copy the application desktop file so the application can be found from the Applications Launcher:
sudo cp -p Firmador-BCCR.desktop /usr/share/applications/
Now you can lunch the app (read note below).
Once the app is lunch you will see the notification and the FirmadorBCCR logo will appear in the system tray. You can now test that is working: https://www.firmadigital.go.cr/verificacion/Verificacion.aspx
Important: For some reason the app crashes when it's launch, launch it a few times(2 in my case) and the app will start. I have not troubleshoot the cause of the start crash.