You are a god send! I have the same issue. My house (2013!!!) is fully phone wired but has zero Ethernet. I have 3 floors which each running on a different phase (the electrician wired it like that). I have a power line adapter in my fuse box to connect directly to the three phases. But I can’t stream content or large files. Even worse the power line adapters bring noise into my power sockets. A guitar amp gets ground crackling etc. will look into this solution!

I see that they also offer a coax solution. Which would fit just as well I have a tv connection in every room which also connects in the second box in the utility room. And I don’t need it ;)