I’m in my late thirties and it was still in common use in India, and perhaps specifically among Anglo Indians? But it meant more like “no chance”.

“Can I go out to the movies with my friends?”

“Nothing doing! You have an exam tomorrow”

Or failure to do something.

“I tried to fix it myself but nothing doing”.

The one from Míšov, Czech Republic is tribute to the running joke of nonexistent genius Jara Cimmrman

https://en.wikipedia.org/wiki/J%C3%A1ra_Cimrman

Was it in a Monty python sketch or something?

The plaque is identical in two of the photos (one from Ireland, one from Luxembourg), and the wording is identical in those two plus a third (from Western Australia). That makes me curious.

You don't think this is just a joke that multiple people thought of independently?

Some of them might be in reaction to a local event, or even a worldwide event that had no local impact. But I think they're mostly just jokes.