The 30-day RV and IV of ETH are not high, around the historical median. You can set up some long positions in the volatility for the long term. A calendar strategy is quite suitable, capturing theta in the near term and vega in the long term.

Specifically, sell near-term call options and buy long-term call options, balancing delta neutrally. Capture profits from theta and vega increasing volatility. Setting it up with puts is also fine, the principle is the same.