I have heard good things about Cryptpad but prefer a classic cloud aporoach. What I find really strange about NextCloud is not having e2ee. You can always encrypt on your device using #cryfs or #gocryptfs and then send to the cloud which in fact is safer for docs are stored encrypted, but I still prefer e2ee to be part of the cloud solution 

 If you run nexcloud on your server with encrypted filesystem, uploading files over encrypted connection. I suppose it's 99% of fully e2ee solution. Good enough for majority of cases. 

 Nextcloud has experimental e2ee right? 

Nextcloud is too bloated and slow to be useful anymore.