I remember a thread where someone had had success with an amzon fire tablet. Took some work but they seemed happy. Do some forum searches here for Amazon fire tablets, and see if you can find it. The 7" ones were just $29.95 on prime days!
Latest gen iPad (not Pro). About the same price as mini which is way outdated. iOS is most stable platform for DJI. It is a little big (though that is also a bonus as well). If the mini had been updated in 2018 I would have recommended it. You can pick them up new for 299.00 not sure about used. Not the cheapest you can find, not the most expensive just like the Mavic Air. It is going to be one of the best, sorta like the Mavic Air.
Don't mess with stuff that you have to hope works or force to work, just not worth it.
I’ve dedicated my old iPhone 6, which was collecting dust, to my Mavic Air and I must say that the screen is a bit tight with the DJI GO 4 app. Also, I’ve had occasional messages about CPU fully loaded, and video breakup on the phone - video recorded on the MA not affected.
I agree about the regular iPad (9.7”) would probably be the way if I’d go if I had to buy something new. They happen to be on sale this week at BestBuy, $299 for 32G version, $399 for 128G. I have an old iPad Mini2 32G so I’m on the fence about going to the iPad, because the Mini still works OK, though the processor is somewhat dated. The DJI app is only getting more computationally intensive.
I am using Acer Ikonia one 7 b1-790. I got it brand new for £40 on ebay. It works very well and fits the controller nicely. I have turned off all the bloat ware apps and 1GB of Ram easy handles Dji go 4 app. Now just waiting on delivery of anti glare screen protector as without it the screen is quite reflective on sunny day.