KitKat was the first version to ship with Chrome as the default browser, but IIRC it didn't replace the system webview or become auto-updating until Lollipop. Wikipedia shows 70% of Android users on KitKat+, and about 35% on Lollipop+.
https://en.wikipedia.org/wiki/Android_version_history#/media...
I dunno what Samsung ships with, when I was still doing a bunch of mobile web work (early 2014) they used a forked version of Android Browser that was really terrible. Hopefully they've replaced it with something saner. A lot of recent Samsung devices have dropped Android entirely for Tizen, though.