To share some recent experiences with this group, I got jealous of all the cable modem folks that were able to swap out their ISP provided equipment so I did a little research and hacking (ATT fiber requires you to use their ONT and gateway/router). I am currently running a Ubiquiti EdgeRouter 10x directly connected to the ATT optical network terminal (ONT), but powered by high quality supplies. It has had a significant positive impact on SQ (I was very surprised, esp. the impact of powering the ONT with a DXPWR LPS).
For those wanting to experiment, the gateway/router does WPA authentication against the ONT to get on the ATT network. The ATT subscription is managed through the ONT (you can't steal service), but the WPA authentication is to force teh gateway/router to be the ATT provided one.
If you have a dumb switch sitting around, you can try the following. Get the MAC address of your ATT gateway/router and clone it to your own router (in my case, my EdgeRouter). Plug the ethernet from the ONT into the dumb switch and your ATT provided gateway/router into the dumb switch, leaving your router disconnected. Once everything is up and the authentication is done, unplug the ATT router and plug your router in. Since they have the same MAC address, the ONT will happily allow it on the network.
If you want to go next level, you can also install WPA certs on your router, and have this WPA authentication happen without having to do the swap trick or having the extra switch in the chain (this is what I do). That is a more involved process, but it eliminates a switch and gives a more direct signal path.
In this configuration, my music network becomes fiber from the street -> ONT (LPS powered) -> ethernet -> EdgeRouter (LPS powered) -> ethernet -> Sonore opticalModule (LPS powered) -> fiber -> Taiko Extreme
Extremely clean (no pun intended). LPS's end to end make a surprising impact in my chain. As a bonus, it has moved my tangle of LPS's and cables from my family room to my bedroom closet (at least a bonus for me...others are not so happy about all the switches and power supplies and cables that have taken over the closet
Note that in these configurations, your router is exposed to the public internet as your internet gateway. Take care that your firewalls are set up appropriately, etc.