Success!!!! I did it as was recommended. Factory reset Router, powered on and connected to the M20-d (via an LAN port on the router) with an Apple ethernet to USB adapter; iPad snagged the network, logged on with the router's password, and the iPad app hooked up faster than with a dongle.
The Belkin router gives several different networks to hook up to; the network named " _ _ _ Belkin.media" is the 5 Ghz network; the one without the ".media" is the 2.4/5 Ghz network. You really don't have to do anything more than that for set-up. Digital-sound had made the recommendation to change the password on the router; the Belkin unit comes with an 8-digit alphanumeric password already assigned (unlike the "0000" assigned to some routers), so resetting the password is needed only for convenience, and can be done with an iPad. The 5 Ghz capability I think will be important, as I've got a Line 6 G30 on the way; hopefully it will cut down on the frequency of app, dongle and sometimes, iPad reboots needed during a gig.
It seems that there should be more thorough, less ambiguous and yes, less incorrect info on the Line 6 website (".. just use a dongle to hookup the M20-d..." from the set up video). for those of us who find it less than intuitive. Thank goodness for all your help here!