Thanks for recommendations. Proton Mail does seem to be highly regarded privacy wise, however they technically don't allow multiple emails (unless you pay), according to their Terms of Service (TOS): https://proton.me/legal/terms

Authorized use of the Service You agree not to use the Services for any illegal or prohibited activities. Unauthorized activities include, but are not limited to: 7. Having multiple free Accounts (e.g. creating bulk signups, creating and/or operating a large number of free Accounts for a single organization or individual);

So, this isn't perfect solution as then you are forced to use the same email to sign up for multiple services, unless you: a) break the TOS b) use email aliasing service which also usually require payment to have unlimited amount of aliases, as free plans are usually limited to just few aliases.

As for the temporary email services, that feels to directly contradict the whole idea of required email address. As whatever the possible positive sides of required emails are, they are likely nonexistent if users are able to sign up using temporary email services (correct me if I am wrong). It also adds just a bit of inconvenience to the user that is signing up. And your account may then be "bound" to that email provider, unless a) you change it to different email (which contradicts the use of temporary email in the first place) b) a site allows you to remove the email. Which does seem to be possible in case of lemmy.world, according to one of the comments here.

There probably just isn’t better “individual” approach than making email simply not required, simply because working around required email is already some “resistance”, whereas no required email is no “resistance”. By “individual” approach i mean that no required email approach is best if you consider it from view point of single individual, not considering the positive sides of required email.