Just use any other email provider that works for you and use standard OpenPGP to encrypt your emails. This is how email end to end encryption (e2ee) usually works.

As long as the emails are properly e2ee, no email provider is “more private” than others. They can always see who your are emailing and when. Proton is still forced to give out all your metadata to the cops just like any other service.

Also if whoever you are emailing isnt using protonmail, or another PGP compatible client, then your emails arent actually encrypted at all. For work emails the other party usually wont be using any of that so there is no point, for personal stuff i would honestly use standard messengers that have encryption built in like matrix, signal, session.

If you want e2ee email tho, then on desktop Thunderbird has all the OpenPGP stuff built in and for mobile there is the K9-Mail client that can be coupled with the openkeychain plugin to offer encryption.

There are also things like DeltaChat that allow you to use email in an instant messaging style format while using the same encryption keys that you use for standard emails. But tbh thats not what email is intended for, i would just use matrix for that.

Protonmail is a decent attempt at offering “easy to use” encryption but by doing so, makes it overly complex from a software security and compatibility standpoint.

With e2ee you want to have the absolute minimum level of complexity and code to make it easy to audit and understand. PGP has been the standard implementation for email encryption for decades. Any attempt to “expand” on this by implementing fancy web based shenanigans undermines the simplicity and inter compatibility of the preexisting email encryption ecoystem that everyone has been using.