Firewall Questions

I just did the install of FreePBX with Asterisk-NAF for GoogleVoice SIP

I assumed I could Install the FreePBX Firewall.

I just found old posts talking about problems with Firewall on Debian, this is running on ubuntu 18.04

When I go to available modules and click on Firewall it says
Missing Requirements:
The File “/usr/lib/sysadmin/includes.php” must exist.
The Module Named “manager” is required.

From what I read here in this thread “Firewall requires Sysadmin. Sysadmin assumes that if you have a licence file” which seems to imply the FreePBX Firewall is a No-go witgh Open Source FreePBX?

Its all so confusing …