Tutanota mail is an alternative to Protonmail, but you can't use another email client like Thunderbird. There's some more options listed in this link:

https://www.privacyguides.org/en/email/

As I suggested before, macaw.me offers free email, and monocles.de offers free and paid encrypted email (both use Roundcube webmail).

Here's a list of email providers that work with Delta Chat:

https://providers.delta.chat/

Here's a list of email providers that work with dismail.de:

https://dismail.de/serverlist.html

I have been on the search for another larger and more developed email provider as a backup for instances when I can't use my other emails because they are blocked by some services or an entity I need to interact with. Here's a list of email providers I have managed to find for you:

• cock.li (Vulgar, but has less vulgar domain name options, and they claim to be more transparent and honest, but I get some right-wing libertarian vibes from this service as I learned about it from Mental Outlaw (yeah, I know I watch some cringey tech channels, but I learn some helpful device from them, which is the only reason why I still watch them on occasion))
• Fastmail (Proprietary, but they contribute to open source projects, and their JMAP standard project is pretty interesting)
• Forward Email (Free/paid and open source, including the backend, and quantum-safe encrypted)
• Mailbox.org (Proprietary)
• Maildrop (Free and open source throwaway email service)
• Migadu (Proprietary, but built with open source software and has some open source repositories (GitHub), but forced free tier users to switch to a paid tier within one month during the pandemic)
• MXroute (Proprietary, but built with open source software and has some open source repositories (GitHub))
• Runbox (Proprietary, but built with open source software and has some open source repositories (GitHub))
• Swisscows.email
• systemli.org (Apparently it's only available by invite link, and you have to be a leftist and know someone willing to give you an invite link)
• Zoho Mail (Proprietary, but has some open source repositories (GitHub), have a good reputation, and also provides services such as an office suite, though their services are business oriented)

Keep in mind I haven't done much research on these email services to be able to recommend them. I am posting whatever I find, and hopefully someone may be able to make a comment or you will be able to research more about them to see if they fit your needs.

Here's a short list of email providers:

https://github.com/cdransf/awesome-email

I'm going to post this as it lists some email resources, testing tools, etc. even though the curated list is more intended for self-hosting email and email design:

https://github.com/jonathandion/awesome-emails

For VPNs, I would suggest using:

• Mullvad
• IVPN