Anyone still having this problem? Old post, I know.
I set up Alexa a little while ago using a very cheap Blackview A70 Pro, which runs Android 7.0. I bought it new a couple of years ago for £70. You can pick up used ones on eBay for under £50. If I were doing it again now, I would use an iPhone 5S, which can also be had for under £50. I never had any trouble installing the Alexa app, Smart Life and the LG TV app on an Android or iOS phone.