EURUSD price = 1.22831
M6E price = 1.2333

Why is there a difference? Shouldn't they be exactly the same?

My guess is: Futures contract = future price (at settlement), FX is spot or current price.

All futures have a type of interest or borrowing cost baked in. Arthur Hayes from BITMEX explains this very well.

If linking to this is not okay then just look up covered interest rate parity.
https://blog.bitmex.com/bitcoin-and-interest-rates/

Other topics of relevance
https://tsi-blog.com/2015/05/the-futures-price-is-not-a-prediction/
https://en.wikipedia.org/wiki/Spot%E2%80%93future_parity