I self fund my Dexcom CGMs and did not get a G6 reader until I upgraded to a iPhone 13 a couple of years ago, as it was quite a long wait before Dexcom finished their testing of this hardware. I now use a G7 and always update my iOS software on time, even if not yet on the official Dexcom compatibility list (i.e., they are still running tests - usually 1-2 months post OS release date). Haven't needed to buy a G7 scanner. Fingers crossed this has been OK for me so far. Planning to skip iPhone 14 (but is Dexcom compatible), maybe see about an iPhone 15 at the end of the year.
Sorry I can't offer any insight re Android devices.