Cozy Cloud is an open source alternative that just got out of beta and looks very promising! Clients for every platform, 5GB of free storage, the data is stored in France, but you can also run your own server at home. I've been using it for a few weeks, works like a charm - only thing I miss from Dropbox is file versioning. https://cozy.io/
This page describes the mastodon.social instance - wondering what Mastodon is? Check out joinmastodon.org instead! In essence, Mastodon is a decentralized, open source social network. This is just one part of the network, run by the main developers of the project It is not focused on any particular niche interest - everyone is welcome as long as you follow our code of conduct!
Hero image by @b_cavello