I think what parent meant was that Euler spent a few decades in Russia because of the funding provided by the empire. He spoke fluent Russian, even though there was a large German-speaking community there.

But it was typical for scientists to travel far for money. Some of the Bernoullis, a family famous for mathematicians, also worked in Russian for quite a while.

Does it really matter who payed 'em and what languages they spoke?

I was just surprised;-)

He worked in Russia more than in any other country and died in St Petersburg being a Russian citizen.

Oh, I thought this was riffing on the "shakespeare, in the original klingon" line.

I wonder what he would have considered himself - he spent more time in St Petersburg than anywhere else but was born in Basel and spent a good bit of time in Berlin. For what it's worth, the Opera Omnia are published by the Swiss Academy of Sciences.