the original developer somehow decided to sell out to the dark side

It’s pretty ungrateful to frame someone who developed and provided software for free for a long time as a sellout.

I switched from Proton to Tutanota for two main reasons.

1. I didn’t want to put all my eggs into one basket, just like you. With Tutanota I get email and calendar in one package. For VPN and online storage I use independent solutions (Mullvad, local solution via syncthing). Related to this, I don’t like paying for a bundle of programs when I only really want to use a subset.

2. Proton isn’t following through all the way. They keep adding services (password manager and captchas recently), but they don’t provide the same experience across all devices. I’m on linux and their drive doesn’t offer a client that syncs my folder with essential documents. I have to manual upload. That’s a dealbreaker for me.