Even if I "hide" the 5ghz, and "forget" the SSID on my android phone

Which Netgear router is this?

Another tactic is to use a cell phone Hot Spot.  i.e.:

• Power off the WiFi router (temporarily, when no one is around to scream at you)
• Configure a 2.4G Hot Spot on a cell phone with exactly the same WiFi credentials as the primary router.
• Use a different smart phone to connect the Mitsubishi product.
• Connect that smart phone to the cell phone Hot Spot.
• Bring up the Mitsubishi app.
• Use the app to connect the product to the cell phone Hot Spot.
• Once the product is working correctly, power off the Hot Spot.
• Power the WiFi router back on.
• When the WiFi router come up, every device in the house will connect to it, including the Mitsubishi product