As a native English speaker, keen feels like a very 1950s TV word. Don't know if that's actually true but feels like that way. I expect you're more likely to hear like cool today are some more contemporary word.
Brits still use the word somewhat frequently, though I haven’t bumped into many of them in the last ten years.
I'm also a native English speaker, sounds perfectly normal & commonplace to me.
Still in common use in Britain as far as I know. A more local (Bristolian) word would be "keener" used to describe someone who puts lots of effort into a task to win praise.
“It offers fewer words for the people directly around you, but more for belonging at a distance” - the further I get into this article the more it just seems like sampling bias as a narrative.
It's still used in a couple of specific senses - it's used in the nearly fixed phrases "keen edge" or "keen mind" as a synonym for "sharp", and as "to be keen to -" to mean "eager". But, in my experience, it's rarely used to mean grieving ("to keen over -"), and almost never as a generic term of approval ("that's real keen").