tcp-xenos

You need to find DHCP options under your LAN settings

DHCP is the service that provides information like the IP address, gateway, dns, and subnet to each of the clients in your network

In this case you want the DHCP server on your router to hand out your Adguard IP address as the DNS

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I would also like it so if my Raspberry Pi is ever down it would just pick up a like normal just obviously with ads.

This is why it has fields for DNS 1 and 2. DNS 1 will be the primary, but if it's not working, devices will fallback to using DNS 2.

If you want to be sure devices will continue to work fine even if your pi is down, put your adguard IP in DNS 1 and then a normal DNS server such as 1.1.1.1 in DNS 2

After you change those settings, open a terminal on your PC and run

ipconfig /release && ipconfig /renew && ipconfig /all

scroll up to find your Ethernet adapter and see if the correct DNS server(s) are listed

That's an easy one

Moca is great

Powerline is garbage

If you really have an existing coax connection between both locations, there's no competition. Powerline adapters are an absolute worst case scenario

10G under $200 is going to be tough.

I'd personally build it with a fanless mini PC like this for even less power and zero noise

They used conduit AND left some slack in the cable? Lucky