Neither the iHome smart plug, the Wemo Mini, or any other smart plug that I have seen will work.

[Rmconcha]

How do I setup a smart plug that only runs 2.4g networks to Alexa that is connected to my Orbi at 5g - or to put in another way, how can I force my Alexa to connect to my Orbi via 2.4g?

[FURRYe38]

Try lowering the power on the 5Ghz radio from 100% to 25%. Long enough to see if the devices will connect to the 2.4Ghz radio. Advanced Tab/Advanced/Wireless Settings

Try setting WPA to OFF to see if the devices connect to the SSID. Then try WPA and TPIK and AES then try WPA2 and AES.

Set a manual channel 1, 6 or 11 on 2.4Ghz.