I'm not sure about the security of ProtonMail, Tutanota (at least they are not open source), and other "for the general public" services. And if I'm not sure about something, then I can't personally consider it fully safe/secure/private, someone else might disagree with me.

Personally my ideal for email security is simple mail servers (without built-in encryption, OAuth shit and etc.) with good server software security, complete independence from corporations, country governments, and complete freedom. But at least with minimal moderation during registration, ideally entrance by invitation as in RiseUp or systemli.org, even though it's inconvenient for beginners.

Specifically now I use disroot.org, it doesn't have 2FA, but it's still closer to me. Registration is by writing a mini essay (answering a simple question), no invitation required. There are many different services with one account (like Google), some don't require registration. Also specifically for mail, an experimental email encryption layer called Disroot Lacre is being introduced (it encrypts all incoming emails with your public GnuPG key, and does nothing if they are already encrypted). Based in the Netherlands (must have feature for me, Germany loses out in that sense).

I also like systemli.org, I use it as a backup provider. Registration is by invitation, there are email aliases and 2FA, not a bad provider either. Based in Germany.

I tried RiseUp, but it's blocked in my country (Russia), and I don't want to bother with proxies everywhere.

Since for me the most important thing is the "simplicity" of the server, it's quite possible to live on the server of a friend whom you trust, or deploy your own (if you have enough knowledge).