Staking Ethereum is not haram. There is no central authority that can declare it so, and there is nothing in the Quran or Hadith that would prohibit it.
In fact, staking can be seen as a form of investment, and many Muslims invest in stocks and other financial instruments without any prohibitions.
The main reason why some people might say that staking Ethereum is haram is because of the potential for gambling and speculation. However, this is not a valid reason, as gambling and speculation are themselves not haram.
What matters is how one uses their money, and if they are using it in a way that is permissible under Islamic law.
So, in conclusion, staking Ethereum is not haram. Anyone who tells you otherwise is likely misinformed or has ulterior motives.