The Superbug Initiative for Two Point Hospital sees players working together across the world, to complete challenges.
These challenges can be done with friends or in larger global projects. It works by progressing through nodes of different challenges like training staff or earning a specific amount of money, with the end result once you've fully completed each line of nodes being some special in-game reward. It's a feature they will continue updating, to add in more challenges and rewards to give players more reasons to keep coming back to the game which sounds pretty fun.
This is a free update, not a DLC which is pretty sweet. If you wish to try it out right now on Steam, simply select the "twopointhospital_patch_beta" beta from the properties of the game to get it. Otherwise, it will roll out for everyone on April 30th.
Additionally, they've added in the ability to add custom music to the game, although the feature to actually create your own playlists and upload them to the Steam Workshop is not yet supported in the Linux version but they did say "We are working on this!".
Great to see it continue to expand after release, I've enjoyed my time spent curing all sorts of weird things.