For MediaWiki and extensions we're using a browserlist for driving eslint-plugin-compat from browserlist-config-wikimedia, which for full compat mode lists:
[
"Chrome > 0, Edge > 0, Firefox > 0 and last 3 years",
"Safari >= 11.1",
"iOS >= 11.3",
"Android >= 5"
]
however it does not. It's passed through as ok, and ends up on old browsers as calling null.