AT&T Fiber speed issues 5-6p.m.

What router do you have?

How are you verifying the speed?

Try turning off 5G. A lot of phones will desperately try to connect to 5G, with higher battery usage, to get less throughput than if the phone just used LTE. The data source often will stubbornly refuse to back down to a lower data rate, making the end user experience worse.

Any time there are power outages, turning off 5G is step 1. Desperation (after parking in a McDonalds lot for their Wifi) is to turn off LTE to at least get texts out without connecting to Wifi.

Are you using wired connection for the speed tests? If not, do that.

Also, the at&t gateway has an internal speed test that you should use, too. You can access this through the web gui at 192.168.1.254 under diagnostics. You may be able to access this through the at&t smart home App, too.

If the at&t gateway internal speed test is low, you likely have a fiber/equipment issue and you need to contact at&t. If the internal speed test is fine, move on to wired speed test.

Connect a PC or laptop directly to the at&t gateway and run a speed test at speedtest.net. If it is low, disable the wifi on the gateway and unplug all other cables to the gateway. If the speed is still low, you likely have congestion issues as fiber is still a shared bandwidth medium and you are likely sharing bandwidth with 32 or 64 other neighbors depending on splitter used. if the speed improves after disabling wifii and removing other connections, then you have something on your network sucking up the bandwidth.

If the hardwire speed test is good, then you are probably seeing wifi speed issues. WiFi typically wont hit 1Gbps even in ideal environments.