What about this?
https://support.t-mobile.com/docs/DOC-28979
https://www.att.com/devicehowto/tut.../id/stepbystep_KM1135186?make=LG&model=G4H810
LG G4, no Nougat on it nor or Oreo. Not a single update since December 2017 for T-Mobile. I get it that zones and carriers are heavy factors in updates. However, it's safe to assume LG ditched support for the G4 since there hasn't been a software patch since April 2017 on AT&T. Neither provided Nougat either.
If Samsung can provide the S6 with some 2018 patches, why can't LG w/ it's G4?
Not everyone upgrades on a yearly basis or every other year basis. One should have to use Android Go, Android One, or a Google Pixel to get long term support. The fragmentation is on Google because they need more hardware and software uniformity. The Windows approach could solve some of the problems.
Apple still pushes updates on the iPhone 5s, a phone that came out in 2013. I am sure many would use Android if there was Apple level support w/ updates and customer service.