My ASUS chose channel 40 and there's only one other user on 40.
Is it as simple as finding an absolutely free channel?
Netspot tells me...
36 1 user
40 2 including me
44 6 user. A whole lot of Spectrum users
48 1
52 1
149 1
153 2
157 3
161 3
165 nobody on it.
It's more than who's using another channel. The signal strength of the other access points is potentially more important. Because of the number of homes near enough to me to detect their signals, there's virtually someone on almost every channel. Using my scanner software, I choose a channel that has the lowest signal level from those other access points. Usually if they're at least 20dB down from my signal level it should be fine, but the higher the power difference the better.
Oh, and don't select channel 52. Your Roku can't see any channel higher than 48 and below 149.
Bump to say that I still think there's a 5G problem with the Express 4k+
My setup is as follows.
2nd floor: ASUS router set to Auto and, 20 feet away, an older Streaming Stick
2.4ghz is 89Mbps 👍
5ghz is 102Mbps 👍
1st floor: Express 4k+
2.4ghz is 41Mbps 👍
5ghz is 5Mbps (basically unusable) 👎
Basement: Streaming Stick
2.4ghz is 32Mbps 👍
5ghz is 23Mbps 👍 (I use this all the time)
Router and all 3 ROKU devices are against a north facing wall along its center.
I normally only use my Stick 4K+ when traveling, but I just pulled it out of my suitcase to test it. I have two different wireless access points in my home. One is in the garage, directly below where I'm currently sitting and where I conducted the test, so the signal is travelling about 12 feet through the floor of the room I'm in. This is my Primary Linksys network router, which connects directly to the Comcast cable modem, so a direct line to the internet for speed purposes. The other access point is a more powerful Netgear AX capable router (even though Roku doesn't support WiFi 6), but it's at the other end of the house, which means a distance of about 50 feet and passing through several walls.
Results: both access points showed a speed test (using the Roku Check Connection function in the network menu) of 192 Mbps. My Ultra 4800, which is within five feet of the Netgear access point, shows about 225 Mbps on the same connection. This appears to be the hardware limit of the Roku WiFi chip, as my home Internet speed is over 900 Mbps (just tested it, and with myself and my daughter both teleworking it still returned 951 Mbps).
My personal take: there's no issue with the Roku Stick 4K+ on 5 GHz. If a particular device is having connection/speed issues on that band, there's likely some sort of interference that is causing the problem. The full wavelength size at 5 GHz is 2.3 inches, and moving a device just a few inches can sometimes clear up issues like this. Other times it takes a change of channel used in the WiFi access point radio. The advantage of 5 GHz is that there's far more channel choices than on 2.4 GHz, so trying a different channel is another option. Just don't choose a DFS channel (49-148) as Roku devices won't work on those channels.