First thing is generally to avoid storage (diversified electric mixed,interconnection, big demand response market, and things like solar not optimized for the maximum kwh generation but for generating kwh when needed possibly...)

Then you have thermal storage ; a big share of the electricity we use is to generate cold and heat, and there are a lot of cheap technology out there for thermal storage. It used to be at the clients place for short duration storage(typically storage eater, and now some ice aircon, but there are much more technologies and innovation, at all scales, which include seasonal storage. Most of those tech use thermal storage then to directly use the heat/cold, few use it to generate back some electricity and then could be part of the next paragraph too...

And there are many different technologies taking electricity (or heat that could had generate electricity) and giving back electricity... Pumped hydro is the biggest and oldest player here, but with some innovation coming... There are also different batteries technologies, and many other more exotic possibilities including piling up some concrete blocs...

Lasard Bank write every year a report monitoring the price of the leading technologies. Greentechmedia is a good source to learn more about the development of these technologies and of the market

Power-to-Gas is in the "works but is not economical" phase of development right now. Pilot plants are up, it's a matter of scaling and optimizing cost. The advantage is that every country already has infrastructure for strategic gas reserves.

https://en.wikipedia.org/wiki/Power-to-gas