Proton does require you to have a dedicated phone number or email to sign up though, like that was my main thing that swayed me away from making a protonmail account was when I went to sign up I was met with a phone number requirement and I'm like "oh well this isn't going to be helpful"
They claim it's to prevent abuse of the service, and that it's only the cryptographic hash which can be used to find out if the email has been used on an account before. But I dislike that it requires even going that info
ammendum: apparently this restriction may be based off of your region used and browser. I was able to finally successfully create an account using Chrome, but Firefox exclusively gave me email or phone number requirements