Everything you need to know about so-called 'Swiss Privacy' we learned decades ago from Operation Thesaurus, AKA, Operation Rubicon. We learned that CIA operations and black budget banking are actually headquartered in the Swiss underground.
If you trust any third-party server to protect your privacy, you're a rube. If you trust Proton Mail to protect your privacy, you're a rube getting 'crossed' by the Swiss Rubi-con. Either you own your keys and your data on your computer or else you have no privacy. Someone else's promise that your data will be 'encrypted' so they can't decipher it is a hollow pledge. If you send any form of plaintext to a remote server, no matter how much they claim to encrypt it, you have zero assurance of data privacy.