
GL.iNet
GL-MT6000 (Flint 2)
OpenWrt enthusiast's choice; good value, but lacks 6GHz.

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In two houses now I have used TP-Link — they have been very very reliable for me. Am currently using 3x XE5300 (AXE5300 set from Costco) I got from Costco on sale last year’s Black Friday or the year before. Have been great. I’ve got them configured in Access Point mode, and connected to my Spectrum Router with the router’s WiFi turned off. Current I’m using the 6GHz channel for backhaul. In a previous house I used TP-Link Deco M5s throughout my large country home (3700 sq ft) plus additional Deco M5s in one small outbuilding (guesthouse) and one large outbuilding (office, storage and workshop) plus a outdoor pool and large deck area. I had the large outbuilding connected to the main house via a Ubiquiti high speed point-to-point wireless. And had all the M5’s connected to Gigabit switches for wired backhaul and PoE. Again M5’s were in AP mode. And the house was served by a 1GB bi-dir fiber feed from the Internet provider. Overall a great set up. If I were installing today in a new to me house, I’d get the TP-Link Deco BE11000 3 pack on sale at Costco right now. In both houses I had 70+ clients including apple PCs, Windows PCs, smarthome (Google, Apple & Amazon), music (Apple Homepod Minis), plus iPhones and Androidn phones & tablets. No issues at all, and support roaming across the mesh.
As a counterpoint, I have a Deco XE5300 system that is rock solid. I recently decided to invest in moca adapters to let me move my server & hubs, as our cable comes into the house in a really weird place. I’ve found the Deco system really easy to use and configure and quite reliable. OP I don’t know if it’s your specific units, or if you have suboptimal placement, or not enough units, but I don’t think there’s some fundamental flaw with this product like which makes it useless.
Yes. I have my TP Link Deco units connected via Ethernet.
Recently moved off my TP Link Deco Mesh X5300 system. Was working great until I was getting consistent drops from a few different smart devices. I went with UniFi Dream Router 7! So far so good. Now converting all of my smart home devices over to Home Assistant with a HomeKit bridge to enable items in HomeKit.
The XE75 is a solid system, I set one up for a good friend a few years ago (XE5300 from Costco) and they have been rock solid for them, their home is probably closer to 3000 square feet, we set them up in a V shape so two upstairs on each side of the house and one centrally downstairs. If you plan to keep the ATT router, just disable wifi on the router and turn these on to AP mode. Couple suggestions, plug them in to the ATT router if you can and plus whatever you can in to each deco unit themselves, even if they are not wired back to the main unit.
> If I could get 50MB/s or faster upload speed in my bedroom Would probably not happen. I have the Deco 6E units (AXE5300) and on wireless 6ghz backhaul, open line of sight in the same room from main unit (wired to internet source) to ~10 feet over to the satellite unit, then running an ethernet wire from the wireless satellite to a PC. Local file transfer is around 30MB/s to at the most 50MB/s. Add any walls to the equation and if the end point device is wireless also, probably going to knock the number down further. I'm looking at Wifi 7 units because of this, 50MB/s as the best possible scenario feels pretty bad when copying big movie files. It's OK for streaming bluray rips but it can have random hiccups if the bitrate is too high.
Get a tri band mesh router set. Like deco wifi 6e or 7. I had 6e were decent and then got a pair of d link be9300's used for $200.

GL.iNet
GL-MT6000 (Flint 2)
OpenWrt enthusiast's choice; good value, but lacks 6GHz.

Ubiquiti
Dream Router 7
Advanced management, but limited Wi-Fi 7 range, SFP+ issues.

Ubiquiti
Dream Machine Series
Comprehensive control, stable for large homes, but slow support.

Ubiquiti
UniFi Dream Router (UDR)
Modular, user-friendly, but tricky advanced setup, poor penetration.

GL.iNet
Beryl AX (GL-MT3000)
Travel king, versatile, OpenWrt, but bulky power adapter.