@frootieeloops What's your ISP internet connection type ? (Dynamic IP, PPPoE, etc.) You can configure the same on your AX12 to replace your ISP router. Unless it's of type that AX12 doesn't support...

@frootieeloops So your topology is: ISP router=>AX12=>your PC - Is that correct ? If you connect only AX12 wihoout using your ISP router - can you do the same test. This web based test seems to be...

@david3 Here's a broader description of the protocols that different TP-Link mesh networks support.

@frootieeloops Can you confirm how did you test the SIP ALG is still enabled on the router after you've disabled it ? Describe your network topology.

@frootieeloops You can try disabling UPnP feature as well:

@sstoichkov According to the Easymesh compatible routers list Archer A6 v4 and above supports Easymesh. Using them the other way round - AX53 as a satellite device would work using the first method.