Just how old an Android device in the developing world do you not want to support? Life's great at the forefront of technology, but there's a balancing act to be able to support older technology vs the bleeding edge.

I like the sentiment, but building a website that can actually function in that setting isn't a matter of mere polyfills. You need to cut out the insane bloat like React, Lottie, etc., and just write a simple website, at which point you don't really need polyfills anyway.

In other words, if you're pulling in e.g. regenerator-runtime, you're already cutting out a substantial part of the users you're describing.

A quick search tells me that firefox 143 from 6 months ago supported android 5 (Lollipop).

So that's my cutoff.

Android phones update to the latest version of Chrome for 7 years. As long as you're using browser features that are Baseline: Widely Available, you'll be using features that were working on the latest browsers in 2023; those features will work on Android 7.0 Nougat phones, released in 2016.

Android Studio has a nifty little tool that tells you what percentage of users are on what versions of Android. 99.2% of users are on Android 7 or later. I predict that next year, a similar percentage of users will be on Android 8 or later.