I'm looking to reduce my dependence on Google services as much as possible, and Proton seems to offer the most comprehensive private suite. A number of things seemed to be missing, but most of my information is from reviews that could be out of date. So I wanted to ask which of these features Proton can replicate.
Thunderbird mail syncing (without paid plan?)
Thunderbird calendar syncing
Calendar sharing
Easy move from google drive to proton drive
Sync android photos like google photos
Offline file saving for specific files in proton drive on android
Sync with folder or mount on linux (smb or similar)
I was in a similar position and moved to Proton. Their native Linux support is rudimentary, but nobody else provides a better, privacy respecting option. Their web apps work well though, and the email client uses local storage APIs for offline use and search.
I do use Mega for cloud storage though, they're e2ee and have solid Linux (both GUI and really nice CLI) and mobile support.