but remember all complaint ethernet is galvanically isolated so as to remove the effects of common mode interference and ground loops from the network signal. Galvanic isolation often uses transformers or can use optical connection, but transformers typically offer better performance in a smaller space. Surges from lightning are handled differently
Chris I honestly would use twisted pair wiring for your ethernet in your house unless you have some very long distances to lay.. sure you twisted pair/phone line entering the house is above roof level - but for the most part a direct or nearby strike will as you say destroy the master socket (as it is designed to do with lightning surge protector that goes short circuit) but even so the lightning current will jump spaces and find the shortest path to earth, If you are in a particularly exposed area you can get specialised earthed phone /twisted pair line surge protectors - but even here a direct hit will still probably cause collateral damage either immediately or hasten the failure of components/devices in the house.
I suggest the only truly safest thing to do is unplug all mains devices with electronic components and phone socket connections, aerial connections - and don't forget Satellite TV coax connections from your STB (which I suspect is quite a source of issues as people forget about it and many STB are not earthed)... then any induced voltages in your ethernet wiring through the ionised air should be dealt with unless you are really unlucky assuming your devices are ethernet compliant