Unable to disable IPv6
I have two eero Pro 6 that are running in bridge mode inside my home firewall. Their sole function is to be meshed access points, and nothing more. I have no want or need for IPv6 on my internal network. The problem is that I am not able to disable IPv6 on these devices. Nothing happens when I tap in the app settings screen, where it says "IPv6 On >", even though it has the ">" there to the right indicating that it is a setting, not just information.
I have already seen that the WAN port will just pick its own IP address instead of using the one I assigned it by my DHCP server when I configure the eero to use DHCP instead of fixed IP, so I can't say that I trust it to not be serving out IPv6 addresses to whatever device connects to it.
How can I get IPv6 disabled on these devices?
The eero does not have an IPv6 server, just IPv6 passthrough. With that option enabled the eero will pass through frames with IPv6 header information, if it is disabled it shouldn't. With the eero bridged it also will not filter any of the network packets, just pass them through (so that IPv6 option won't do anything in a bridged setup). Also, you will want to make sure that the IPv6 addresses you are seeing are actual external addresses, those typically start with a number two '2'. If the addresses start with a 'f' those are self assigned addresses and aren't actually doing anything. Same as an APIPA ipv4 address (the ones like 169.254.x.x).
You said you were trying to get the eero on a particular IP address. With DHCP enabled the gateway eero will automatically take the x.x.x.1 address for the subnet (for example the eero's default subnet is 192.168.4.0-192.168.7.254, the gateway eero automatically takes 192.168.4.1). If you are trying to get the eero on a particular IP address range you will accomplish that in a different way. If so let me know what address range you are wanting to use and I'll provide instructions tailored for that range.