There seem to be updated stats here: https://composables.com/android-distribution-chart

Which seems to indicate about 4.8% are below Android 9.

But also, Firefox for Android still supports Android 8, of which there are 1.7% below.

There's a discussion to be made here about who is dropping support for these users, is it Google (and especially Apple, who doesn't allow other browsers on iOS) or the site owner? Especially given how insecure it is to use outdated browsers.