Arabic, French, English, Chinese (mandarin), Russian.

Seems like something that could fit here

https://wiki.rossmanngroup.com/wiki/Main_Page

NextCloud is straight up unusable to me no matter how much resources I was throwing at it.

OpenCloud seems promising. I would definitely like to play with it a little. I would also like to check check how can I help with a thing or two there.

This seems like a similar story with matrix Synapse vs Dendrite.