ConcernedApe said multipalyer update will be coming in a month if everything goes well.
I wonder if GoG users going to get this update via Galaxy or Local
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https://twitter.com/ConcernedApe/status/983762007466770433

It just launched on Steam, they said we will get it on GOG in a few days (most likley via Galaxy beta feature).

Sorry for asking but when the beta became aviable (if it became aviable) where i have to download it using galaxy? i havent seen a beta tab (even if its empty)

stardewvalley.net/blog/

How do I opt into the beta?
Currently the beta is only available to Steam users. GOG users will gain access in a few days.

For beta on steam u have to join a beta channel!

Every game in the Galaxy library has a "Settings" page on the More menu, and on that settings page there is the option to opt into any beta channels that are available for the given game. Presumably this is where it will appear once it is available, however nothing is showing up for me yet.

there is no active gog beta yet. but the rate the bugs are being reported and fixed (daily), i'd say by the time gog does get beta, it will be time for the full release. if the urgency to get the beta is to take part in the testing, then fair enough, it should be here asap. however, if the interest is playing a working version of multiplayer, i'd say not long now. in any case, the beta will only be delivered client-wise considering how quick everything is being reported and fixed. it wouldn't make sense to release the beta as offline installers.

I am a bug hunter, il love to search for funny bug, thats why i'd love to join the beta testing :D

I activate the beta option in gog galaxy and Stardew Valley is now on version 1.3.8.85907.

The beta is technically "private", but the password was posted on the official blog, "jumpingjunimos". Use that in the Private Channels option to enable the beta.

So, there's no beta for the linux players?

Dunno, but i didnt find a galaxy version for linux. So i assume linux got to wait for full release.

Their official stance is “yes, eventually, but not anytime soon”.
Also, on Linux, multiplayer will most likely be limited to LAN only, as everything else seem to rely on GOG Galaxy.