Not long to wait for the proper stable version of Stardew Valley's Multiplayer Update, as the developer confirmed today that it will release on August 1st.
Here's what they said:
The Stardew Valley Multiplayer Update will be out for PC, Mac & Linux on August 1st!
They also sent out a trailer for it:
Multiplayer isn't the only addition in this coming update, as it also brings along a bunch of new content for the ride too. Bring up to three friends, marry them (or not, whatever) make them a place to sleep and let your farm grow. Such a ridiculously sweet game, fantastic to have it on Linux.