Believe it or not Gameranger wasn't always the only solution. There was/ still might be a fix on a forum elsewhere that while it required you owned the game (or pirated it) you could download a modified exe that would look at a new master server and was still compatible with unofficial patch 1.3. I'm surprised gog didn't know about this or try using that as a basis or even tried contacting them about hosting it. I sued ot use it because it was much more stable than Gameranger which had a few issues

I forget the name but the exe was named something like swbfspy.exe or something. I use it and it works great.

Pretty sure that SWBFSpy's numbers were worse than gameranger. As much as people tout how great every other alternative is, GameRanger was the one to find quick, easy and popular games (somewhat). I tried all the other alternatives and didn't find as many people, this is even iterated by other people's experiences.

This is why the GOG Galaxy/Steam Update is so prominent. It's now a centralised Multiplayer game now. Hopefully the bugs are ironed out quick enough for everyone to be able to connect without any extra nonsense.

Yea SWBFspy was around for ages, the MP for SWBF2 was always there, just a lot of people didn't know about it so there was a player base of like 20.

Yes the only thing GoG had to do was changing the master server address in the original server executable. (you can change & find it with a hex editor)
Something like this:

Find:
%s.ms%d.gamespy.com
Change to:
%s%d.gog.com0000
Find:
%s.master.gamespy.com
Change to:
%s.master.gog.com0000
Find:
%s.available.gamespy.com
Change to:
%s.available.gog.com0000

I don't know which address the gog master server uses so master.gog.com might not exist, but they only need to replace it with the url their master server uses. (I think multiplayer.gog.com??)

From what I heard they went beyond that so that they can guarantee a working anti-cheat environment for MP

Actually this reminds me how HPC and Halo Custom Edition got a community made patch that allowed it to look at new master servers. It was actually a painless update too

The OP is probably referring to SWBFSpy's predecessor, GameMaster, which was replaced by SWBFSpy about a year ago.

You can also install SWBFSpy using a hex editor like HxD by opening your original executable and replacing all instances (ctrl r for the menu) of gamespy.com with swbfspy.com