Which game?
All I can see is this one Rogue Trader, which has not even been released yet, not even for pre-order. What am I missing?

If you pre-order via https://roguetrader.owlcat.games/ you're eligible for beta access.
This was, apparently until recently not possible through GOG but I've just checked and you can indeed generate and redeem the key for the beta on GOG now as well.

Seems to be only available through Galaxy though, no offline installers listed in the library.

It's been more than 24 hours, and the problem persist. What the f*ck is this service CDPR?

Oh, I didn't know that. Thanks!
And now I find it a bit annoying that this beta access feature exists, but only for Galaxy users. Come on.

Weekend service maybe no one is at gog hq.

Correction/addendum: It would appear that Robinson's Requiem cannot be installed via GOG Galaxy, yet the offline installer seems to work fine

Update: I have now oredered a T-shirt.
Feel free to use this to make your own.

I can't even open the installer ...

"Connection to Communication Service was lost and could not be restored!
GOG Galaxy will now shutdown."

Never assume malice when incompetence or disaster is more likely. Maybe it's a flooded basement. They'd be legally required to post on a data breach.

Do you folk know what GOG's setup is?

I'm no expert, so feel free anyone who knows better, to correct or expand on the following.

GOG some time back changed to using a referrer known as CDN, that acts like a middle man. That would have been a huge undertaking, and we are sometimes still feeling the issues related to that, with some links not working or returning what we need. This has slowly gotten better over time.

So this latest issue appears to be related to issues with the server(s) that the CDN operate through.
It has nothing to do with game files GOG have on servers and server backups, which remain untouched. It is just a matter of an issue with ratification and delivery. They appear to be trying to reroute things, or may in reality just be waiting for the issue to resolve itself, but need to be seen or thought of as doing something.

Many of us normally have access to different GOG servers for downloading, as the load is shared around the world.

Running servers and backups is quite costly, and so probably unrealistic for them to have an alternative in place of CDN, that will for the most part be rarely used.

GOG have alerted us, because they are the ones facing any backlash and potentially lost customers and sales.

So just like when your power goes out, you just have to be patient and wait in this imperfect world.

The Witcher 3 complete edition is also stuck at 91.9%. I'm downloading a 50 GB update, so I don't want to redownload it again.

WHAT SHOULD I DO?

It is weekend! /s :D From my own experience CDP is not prone to work on free days so much. :P

On a situation so severe such as the current one, if you want to continue having a job on Monday, you better volunteer and show up to work today and possibly tomorrow and see how you can be of help.

If they can’t turn around things quickly, GOG is so screwed. This possibly changes a lot of future deals with publishers, plus it’s all turning into a circus fast.

This is a sad moment for DRM-FREE.

Whether to provide beta builds via offline installers or not seems to be something the corresponding developer decides, not GOG.
Baldur's Gate 3 or Steelrising, for example, had or still are having beta offline installers available, because Larian and Spiders respectively must have had agreed to this.
It is what it is.