Already this is a problem as I have 1.5Mbit internet.
also dear god I hope it's a typo and you meant 1Gb
You want to stick with moca 2, and there might be some gotchas with older coax wiring, but I previously ran it for years without issue.
Traced the cables and the only splitter I can find is a moca 2 aware one, and the coax cable that would have been used for cable internet is unplugged so that's not interfering.
Nice when it works, real pain to troubleshoot when it doesn't.
This fixed some (probably modem specific) problems where internet would randomly drop in the presence of moca.
I believe you when you say you can't replace them, but I'm curious why? Every wire I've ever seen run through concrete was in a conduit that could have replacements pulled through it. Did they just run the wires and pour over them?
The obvious downside being the extra expense of media conversion.
2.5Gbps isn't even going out of spec for cat5 and should go the full 100 meters.
When everything else fails, ask an RF engineer. Metal is for RF like glass for light.
This is a recurring question and one often answered by “people rent houses/apartments and can’t just run cables through the walls”.
I’m not all that sure what I’d use this specific technology for over Wifi but I can understand why people don’t use wired Ethernet.