Hello - I recently replaced my Comcast gateway with an Arris G36 modem/router, as recommended by various people. I was able to hook it up and establish connectivity to all of the home devices. The G36 doesn’t seem to have the same reach as the Comcast equipment, but in effort to save some money on my monthly bills, I was willing to see it this move will be effective.
The only real problem I have relates to the signal not reaching my detached garage/workshop (~30 yards from my house). In addition to the convenience of having a WiFi signal in this space, my garage doors are connected (via WiFi) to the “MyQ” interface, allowing me to open and close the doors, access diagnostics, etc. The G36 simply does not reach the receiver/s.
So, I performed some research. I should say that I’m no longer a tech-savvy guy… the world of technology has proven to be much too fast for me these days! That said, I don’t think solving this problem should warrant a degree in networking 
So, I purchased a “TP-Link AC1200 Wireless Gigabit Access Point | Desktop Wi-Fi Bridge | MU-MIMO & Beamforming | Supports Multi-SSID/Client/Range Extender Mode | 4 Fixed Antennas | Passive PoE Powered (TL-WA1201)” https://www.amazon.com/dp/B08SBXVSF3?ref=ppx_yo2ov_dt_b_product_details&th=1.
My plan was to run cat6 ethernet wire from the G36 (on first floor in the center of the house) down, into the basement. I would position the TP-Link on the ceiling near a window on a wall that is closest to the garage/barn and use it as an “Access Point”. The hope is to extend the signal closer to the detached structure, so that I have WiFi access and a working garage door interface again.
Dry-run: When I hooked everything up on the first floor, in order to see if it would stretch the signal, what occurred was a complete signal loss form the G36 to all devices in my house. It seems as though when the cat6 ethernet cable was plugged into the ethernet ports, the G36 WiFi signal was disrupted. I tried this in both the 2.5GHz port and in one of the the four (4) 1GHz ports.
I am at a loss. I have attempted to locate some troubleshooting videos, guides, etc., but to no success. I hardly ever post to discussion boards, but this seems to be a very knowledgeable forum… my fingers are crossed. Thanks in advance for any input you may have. -Andy