I use proton accounts in a compartmentalized way for different purposes. One for my real identity and business, one for VPN that is separate, on for an anonymous account etc.

One trick: Sign up for a free account separate from your main account OVER TOR using their onion site. Make sure it's a free account. 

If you try to pay for an account at sign up you will have to use a debit card initially. If you upgrade from a free account, you can use cash or Bitcoin!

Sign up over Tor on the Proton Pass page and you don't have to give an emal. 

There is an option when doing it this way (on the Proton Pass page to create a free account and they will automatically create an email for you.

Then, upgrade using Bitcoin or cash and there is no worry of "having all your eggs in one basket".