Rover #522 featured the cover and main story
Ned Kelly: Outlaw from the Outback. In fact a number of British boys weeklies had Kelly Gang stories like
Look and Learn #462 (1970),
The Victor #367 (1968),
Lion (29 January 1966),
Valiant and Knockout (7 September 1963), so he's story in the Commonwealth is pretty muted covered with interest.
As for the armour, Ned and the Gang actually came up with the idea not from medieval knights but from the book
Lorna Doone and seeing a travelling display that showed Chinese armour in the town of Beechworth during the late 1970s.
While the Kelly Gang story may not be general knowledge to most Americans, for those in the creative field they would very much be aware of his significance dating back to at least 1906 when the world's first feature-length movie
The Story Of The Kelly Gang was produced and distributed.
But my focus is on comic books such as
The Kelly Gang Rides #1 (1945),
Gangster's Can't Win #1 (1948),
The Westerner Comics #25 (1950),
Dead-Eye Western #11 (1950),
The Authentic Story of the Kelly Gang #1 (1956), etc. all the way up to the Swagman in
Batman R.I.P. #676 – 681 (2009) where there's a direct link back to Ned Kelly, his story, and/or his armour...
https://www.folk2super.com/gallery/#comic-batman-rip-009
https://www.folk2super.com/gallery/#Western%20Hero%20#101
https://www.folk2super.com/gallery/#Monte%20Hale%20Western%20#58
https://www.folk2super.com/gallery/#Dead%20Eye%20Western%20#11
https://www.folk2super.com/gallery/#The%20Kelly%20Gang%20Rides%20#1