While not every wiki page has it enabled I find that the simple english really helps my understanding. For ex:

https://en.wikipedia.org/wiki/Probability_theory

https://simple.wikipedia.org/wiki/Probability_theory

https://en.wikipedia.org/wiki/Advanced_Encryption_Standard

https://simple.wikipedia.org/wiki/Advanced_Encryption_Standa...

I once edited a Wikipedia article on an Einstein paper to make it much more clear. It was subsequently reverted. I understand the need for brevity, but the domain experts at Wikipedia revert many seemingly irrelevant edits.

The edit I made was to explain how Einstein made the leap to E=mc^2 by including the step that showed how E=mv^2 for particles of a given velocity. Of course this is well known to every engineer and physicist, but the article on the proof was so hard to follow without it.

Sometimes there will be a Simple English translation for math articles. Here's an index of articles on Cryptography: https://simple.wikipedia.org/wiki/Category:Cryptography