The only social network? How about the Fediverse? Spin up their own PixelFed (and a Mastodon instance too), promote it widely, and donate some of their public money to these FOSS projects based on open standards, instead of just choosing a proprietary centralized platform.
There's no reason social media shouldn't be more decentralized and federated. European institutes can and should consider open source, federated alternatives unless they want to be forced to play by the rules of the big social media providers.