@AugTech figured it out with trial and error. band steering needs to be off. I already had a 2.5Ghz only network. Connected to that and got over 100Mbs (up from <25Mbps). Created a 5.0Ghz network...

Desktop PC, USB 2.0/3.0 ports, Windows 10 Pro updated, desktop about 3 years old Using AX1800 - Archer TX20U-Plus - hardware version is 1.6 Adapter plugged into blue 3.0 port. Using fast.com and...