I hung around with some Aussies and NZ’ers quite a few years ago. I know about marmite and they ate it... sometimes with peanut butter and other stuff.
I have limits.
It was quite a long time ago that I was turned on to Marmite by some Brit colleagues. I was elated years later to find it in an exotic specialty grocery store. Even later, I found that Amazon carries it, and nowadays I wouldn’t be without it, Any time I make a sandwich, I put it right on top of the butter. A little goes a long way. But I find it blends well with anything else I decide to put in the sandwich.