@Skywalkerr.
A very interesting outcome, if you know the IP address (IPv4) you can tracert to 8.8.8.8 so basic connectivity doesn't drop (consistent with no lights going red).
I would factory reset then swap the routers so the Community Fibre supplied router connects to their fibre converter (ONT) and your device is connected to their router. This may or may not help but will aid any further discussions with Community Fibre's support people.
As for the point "the hub didn't come up on their system", I think my Community Fibre Linksys is generating traffic to:
about every 30 seconds.
Also (probably) dcs-global.samknows.com less often.
My guess is one of these (perhaps Samknows) goes to Community Fibre's monitoring and may be specific to Community Fibre's "special" software.
If disabling IPv6 didn't help (on the LAN side) is it possible to change the DNS servers used by the router?
This suggests it might be:
How to change the DNS settings on a Linksys Smart WiFi router
www.linksys.com
My router is in "bridge mode" as I just use it for WiFi so I don't have much in the way of settings available. It's also a more limited model than the current issue.