Quick answer
Multiplayer and co-op status
The official Steam store lists Single-player, Steam Cloud, and Family Sharing, but no online co-op, local co-op, or multiplayer feature. Each farm and story therefore belongs to one local player save.
There is also no announced multiplayer release date. Treat videos, forum posts, or search snippets that promise official co-op as speculation unless NPC Studio publishes the feature on its website, Steam news, or official social channels.
What about multiplayer mods?
A mod labeled multiplayer is not the same as supported co-op. It may break after patches, require every player to use matching files, or fail to synchronize quests, time, inventories, and festivals.
Back up the save before testing any unofficial networking mod. Do not assume Steam Family Sharing lets two people play the same farm together; it shares access to the game, not a live session.
Where to check for an official change
Check the Fields of Mistria website, Steam news feed, and Steam store feature list for official changes. If multiplayer is announced later, this page will separate the supported player count, local or online mode, platform limits, and save compatibility.