What kind of online storage? From the FOSS ones I prefer, I mix up Syncthing for some private documents and for public IPFS.
For some examples on what I have there, my website has IPFS.csv with a list and issue on some more I should advertise on a separate page. I especially like how I don’t have to store binary files on Git and if my chosen gateway would go down, it’s one (or three) line(s) to change in _config.yml.
I hear that Tahoe LAFS would also be good for storing private files and if I just had to share a private file, I would probably try OnionShare (onion) with Lufi (Disroot example) as worth mentioning.
Maybe it’ll be better with new client app versions