Proton isn't opsec, it's just the best available commercial clearweb host that still has to follow all the laws and comply with warrants, but won't be arbitrarily selling your metadata or engaging in the adtech garbage.

Kagi is to google as proton is to gmail.

You get web mail, custom domains, decent security, decent spam detection, solid features, and no PII being sold. Nice, clean, simple - I like paying them money. I feel good about doing business with them, and I don't run into that often these days.