The thread title reminded me of this recent thread
»how to ensure PDF file viewing does not "call home"...
where firewall rules were often mentioned as a cure/fix.
Firewall rules will often prevent a call home function but it's not guaranteed.
It's just a layer.
The only way to guarantee that won't happen is to physically disconnect from the net.
Disconnecting doesn't necessarily mean a call home won't occur on reconnection but it can & should be considered as a legit security layer.