To replace everything. Mail, calendar, drive, vpn, password manager, documents etc. What are the pros and cons relative to proton? What are the mobile apps like? What assurances do you have they won’t go full proton in the future? And other questions
I wholeheartedly agree with Tuta over Proton Mail!
And to add to password manager, KeePass + SyncThing is excellent if you need to access your vault on multiple devices without any 3rd parties involved.