[hdjfkfbfbr]

So what about fibre Ethernet ??? You might be able to squeeze a bidirectional fibre (single fibre which uses 2 different frequencies of light for tx/RX) next to your coax runs through your walls? Then all you need is a media converter / switch on both ends...

[hdjfkfbfbr]

You can go cheap and do 1gbps with fibre too... Failing thst maybe try super thin ether net cable in the same way???

Edit: spelling