[Kalium]

There is!

It's just so far proven to not be as large as one might hope. Consumers, when faced with services that don't offer them the features they want and higher prices, often think twice about preferring privacy.

There's a lot of money to be made by someone who finds a way to deliver the full-fat experience consumers want at the prices consumers are used to while also respecting privacy. Until then, I expect things like Purism and Protonmail to stay fairly niche concerns.