This may be an old response, but I'm currently using the Amazon Fire Tablet HD8 for over a year now, and it works pretty good. A bit laggy when selecting between channels, but it does the job.
I too was using my iPhone XR as the remote, and it sucked.
I'm considering the Helix Floor or LT, cuz the Firehawk 1500 is a heavy S.O.B; I have the carrying case (with the wheels), and it suuuuuuuucks lugging this thing around up-and-down the stairs, onto the stage, in-and-out of the car...jeeze.