Just discovered CryptPad via the FLOSS Weekly podcast. Basically, Google docs without privacy concerns.
CryptPad in their own words:
"CryptPad is a private-by-design alternative to popular office tools and cloud services. All the content stored on CryptPad is encrypted before being sent, which means nobody can access your data unless you give them the keys (not even us)."
It's also Free software.
Better still CryptPad is on the Fediverse:
CryptPad provide a hosted service that is fully featured, but restricted to 50MB storage. If you want more storage they have paid for subscription plans.
However, as it is Free software you can host it yourself:
https://github.com/xwiki-labs/cryptpad
You can hear all about CryptPad on the FLOSS Weekly podcast:
https://twit.tv/shows/floss-weekly/episodes/532
The lead developer is also on the Fediverse:
@ansuz@social.privacytools.io
Disclaimer: I've had a play with CryptPad, but not used it for real in a collaborative session.