If you want your desktop QB to never ever communicate with the internet in any way at all, this "might" work on PC's:

Control panel>systems and security>windows defender firewall (click the main title “windows defender firewall”, not any of the subtitles)>advance settings>outbound rules (because evidently our computers actually go outbound to communicate with quickbooks when using it or something like that)>new rule>program>next>browse>this PC>C (or c drive)>program files (X86) (it is possible that your exe file will be under the regular/non-X86 plain “program files” instead)>common files>intuit>quickbooks>QBWebConnector>QBWebConnector.exe>next>block the connection