There are a fair few instances of English folk melodies where you could posit a major 7th. Towards the end of The False Bride melody (as printed in the Penguin Book of English folksongs). Or in The Brisk Young Widow. (If I can ever manage to play it properly, I've got a sort of Western Swing version of Brisk Young Widow, with a fair few major 7ths in it, which I'm quite proud of.)

A lot of Northumbrian clog and hornpipe music from the late 19th century has, it could be argued, implied major 7ths at times. Which makes some kind of sense, as we're not far off the influences of American ragtime.

I use the words "implied" and "posit" very deliberately here: we're talking essentially monophonic music. It could be argued, if you wanted to, that any chordal accompaniment that's too assertive (major, minor, dominant, diminished) is squashing the modal nature of most of the songs we're talking about here.