Syngas (infinitely better than hydrogen, which was always a stupid idea), or huge-scale Carnot batteries (the square-cube law is your friend) would do the trick nicely in both cases.

Syngas has the problem of where do you get the carbon. With hydrogen, the exhaust (water) just gets released to the atmosphere. Syngas would require capturing and storing the CO2 of combustion for reuse in making more syngas, which adds to the cost.

But yes, resistively heated ultra low capex thermal storage ("hot dirt") is very attractive.

This assumes prices for the solar panels and batteries continue to fall as this build-out happens. I don't think it should or could happen in a single year, but slowly over the next 5-10 years.