The release date of build "multiplayer -4f" is on the same day as the official multiplayer release on steam. These were the last updates by OG devs on both platforms. Thus I assume it's the official build, even tough it's under the beta channel on Galaxy.
My assumption is that the OG devs forgot to switch to the main channel when uploading it to gog. In addition, in less then a week after that they announced the paradox takeover. One more reason to believe that they just rushed the build to gog without taking the time to move it to the main build channel.

Refer to the release date in both gogdb and steam update links I posted earlier.

So my assumption is that "multiplayer -4f" is feature complete in terms of non multiplayer content for sure. In terms of multiplayer functionality they either forgot to moveb it to the main channel or they had to do some gog galaxy specific multiplayer additional work before doing that, which never happened because paradox took over in the meantime. Either way, I believe that this is the most feature complete pre paradox build which gog ever had.

Cheers

Update:

Got an answer from support, which i find extremely annoying to be honest.

Basically the first sentence is stating that builds "multiplayer -4f or "15b" are not supported and offline installer can not be provided.

Then the second sentence is telling me that it is available through Galaxy (hence supported). And i already stated that i know that it is available through Galaxy. WTF?!

So if one does not want to use the "optional" client of a store which markets itself as drm-free, then enjoy the 3rd class citizen treatment.

No comment. I actually expected to get from support the installer tbh. Have heard of cases where they send older installers to owners of game. Instead what i received was answers making no sense given what i was asking(in the style of: Q: Whats the time?, A: The sky is blue.).

P.S. I dont know if its ok to copy and paste the whole conversation. Thats why i am not doing it.

Update 2:

After some additional back and forth i got streight answer in the end from support (and thank you support for providing such in the end).

Last answer summary:
They cannot provide me with offline installers for the builds "multiplayer -4f" and "15b".

So thats that. However, even though offline installer for build "15b" is not available from GOG, its available elsewhere. Do what you want with that info.

Obviously they could provide an offline download since it’s available on Galaxy after all, they just don’t want, let’s be honest. While GOG is still clearly my favourite platform, I’m afraid it may change in the future, because of that Galaxy frenzy that makes them look more and more Steam-like… up to some point where the difference between the two may become blurred enough that there’s no more interest in staying here.

The way it currently works, I will never accept Galaxy (and it should never become mandatory anyway).

Thank you for trying, this is exactly what I expected from GoG.

Looks like I will have to accept that the version I have not being the last Introversion one which is a pity :'(

I had originally bought it on Humble Indie Bundle (back when they existed and were fantastic) well before GoG had it and as I wrote above I never knew it was sold to Paradox before it was too late to get the last Introversion version.

I checked on Humble and surprisingly it was all updated there. I kind of expected Humble to have the last Introversion one as that indie bundle was a while ago ...... but I guess it is Kudos so the people who bought it there in the first place still get updates.

I'm just checking it now because perplexingly, it is a huge 6.3 gig download. It is because it has linux mac and PC files and in 3 subdirectories gog steam and vanilla whatever that is.

The thing is the Vanilla and Gog one the file is "Prison Architect The Jailhouse 1.00" and the overall 6.3 gig file is called pa desktop jungle 10965 and the date on everything is 15/12/22 so there is no way the last introversion one would be there sadly. It was my last chance but sadly not to be. I never expected the humble indie bundle purchase I made so long ago to have anything past the Introversion versions.