MotherShipton I used the Github links for the up to date releases of Mail and VPN in Obtanium. Unfortunately, the Github page for ProtonDrive does not link to any actual releases so I don't see how to use that in Obtanium.
You can actually set these up in Obtainium by using the URL links for the download pages.
Drive:
https://proton.me/drive/download
Calendar:
https://proton.me/calendar/download
Just tested them before writing this, and they seem to work as far as I can tell. Can't really say how well they work with updates though until there's, well, updates for the apps. And the "version" displayed by Obtainium is a seemingly random string of numbers.
Try it though and see if you have any problems with it. As for any kind of change logs, I'm not really sure if there are any.