I understand what you say, however if you want to access to other website in this world you need to create other log in credentials, therefore I prefer to rely on protonmail and know what is going to happen with my data rather than any other provider.
In order to resolve your concern, protonmail could simply create an avatar with the info you like that a user can use for these types of login.

If protonmail provide an authentication process for any new platform, start up or website and the process is managed and designed by protonmail, I believe the respect of privacy would be more likely.

If you wish to make this world better you need to provide better alternative to users. If you do not, I can`t blame users that rely on other service providers that steal their data.

Most of the current Oauth providers are all social media sites. Would be great to have this feature for SSO from a company I trust.

It could also help promote ProtonMail by getting more people aware of the alternatives.

I don't think you understand how severely that would destroy the privacy offered by Protonmail.

I do understand that you want a common account to log in to various sites, and that is a valid request considering the market dominance of Google and Facebook. But Protonmail is NOT the appropriate service to provide common logins. I know that there are some authentication providers out there, but I have not looked recently. I heard about OpenID, but I also vaguely recall that the service was discontinued or became unreliable.

Anyway, please try to learn more about on-line privacy and the different ways that you can jeopardize it without realizing.

`protonmail account` to log in on any other website.

When you try to log into some websites they give the opportunity to sign up or to log in with an existing google account or fb account.
Why not trying to offer the same with a protonmail account? that would make me more confident my privacy is more respected.
I would like to see the possibility to use or not, this feature in protonmail.

I am also building a platform and plan to have quite a lot of users, or certainly reach out 300k potential users with mkting campain.
I would love to allow my users to log in with a protonmail account or even force them to create a protonmail account in order to use my website.

That would help protonmail to grow its users and users would have their privacy respected.

I think it would be great, if ProtonMail would provide an OAuth 2.0 service.
This would be my main login for all my profiles on the web.