I have been looking to de-Googlfy (its hard) and don't agree with many that say "email has been solved" -- there are a lot of different elements that need to be balanced - privacy, usability, integration, User interface. For one of my accounts I am using MailFence (have not seen it mentioned). It is better privacy than Google but less than Proton.
Email Privacy - this topic needs a deeper dive. There are many points where email is exposed (I am not an expert so correct me), most concentrate on your stored mail but mail in motion is a big risk too even if you use Proton or others
- your device to your ISP (mitigated by a VPN)
- the sending email server (ProtonMail, FastMail, etc.)
- the servers along the way (the contents may be protected but not the envelope)
- the receiving email server - if you send emails to people on Gmail, google sees it
I only post that by way of saying the more we get EVERYONE off google the better!