见马克思 ("to meet Marx"): is it used today? I am writing a paper about machine translation and I am looking for a phrase in Chinese that is ambiguous and cannot possibly be translated correctly without knowing the correct context.
I found this article about euphemisms in Chinese which mentions the phrase &quot;见马克思&quot; in the sense &quot;to die&quot;.
Is this phrase really known/recognizable by an average Chinese person? If not, are there any better phrases with ambiguous meanings?
Sohu has a news article dated from 2020-07-26, with a sentence that reads:

腮部中弹，离大脑很近了，稍有不慎，杨勇恐怕就提前去见马克思了。

Here “见马克思” is used to mean “to die,” like what was mentioned in the question above.
The phrase in question is featured in a recent write-up by a large company that services the Chinese speaking world. I think it is fair to say that it is well known enough for the editors to leave it in without thinking that it would cause confusion for their audience.

The bigger problem I see with your question, though, is the fact that many machine translations use dictionaries and the phrase in question can be found in quite a few resources.
见马克思 can quickly be found in five Chinese-English dictionaries:

ABC
Pleco C-E
KEY
CC-CEDICT
Wiktionary

One Chinese-French dictionary:

KEY French

And one Chinese-Chinese dictionary:

现代汉语大词典

The longer term 去见马克思 can also ben found in one Chinese-German dictionary:

HanDeDict

As far as I can tell they all contain the euphemistic definition, “to die.” It shouldn't be too hard for a well trained machine translation to be able to translate the phrase correctly with the right tools.
There are a lot of bad Chinese translations, seemingly curated by machine translators, online, i.e.: Bubbles | 20 of the Best (Worst?) Chinese Sign Translation Errors &amp; 干 has always been an issue. You might find a more appropriate example in some of these resources.