For e2ee you might want to have a look at CryptPad (https://cryptpad.org). You can test it on the free instance https://cryptpad.fr

You'll have plenty of doc types with full end to end encryption, including for your drive.

We plan on getting e2ee as we have the military are interested in using it. From what we investigated there will be some tradeoff feature wise (attribution of edits will be harder for example). Happy to receive some help on that front.

A while back this was posted on HN - https://github.com/docmost/docmost/

No, but the French and German governments just gave you an excellent code base to start from!