F5 Application Services Templates gui not loading

Have you manually downloaded and isntalled the latest RPM package ? Better do that before doing any dipper investigation https://clouddocs.f5.com/products/extensions/f5-appsvcs-templates/latest/userguide/ , also from what you say better chek https://clouddocs.f5.com/products/extensions/f5-appsvcs-templates/latest/userguide/managing-templates.html as it seems the system is trying to update the RPM but as you said the firewall is in the way.

Also no one outside of F5 can tell if the 104.x will change in the future, so you can raise a P4 support case and just ask and see what will the reply be.