If you pre-ordered you were upgraded to DD automatically. You'll know if you have it if you click on BG3 in your GoG library and see this (enclosed photograph).

Hasn't worked for a lot of people who pre-ordered, still waiting on GOG to address it other than this support post which hasn't worked: https://support.gog.com/hc/en-us/articles/12642618490525-Where-Can-I-find-Deluxe-Edition-DLC-upgrade-?product=gog

If you had the game in early access you should have the deluxe upgrade. I do.

But maybe if you bought it very close to launch there's a delay of some kind.

I bought BG3 same day early access started around 3 years ago, and I am still waiting for my DD goodies.....

GOG says you don't have it or you just don't know how to find them in the game?

Because most of the items are at the camp.

I also bought BG 3 three years ago and didn't get the Delux Edition. Not only that, I see that the GoG version also has a delay with game updates, and some problem with achievements (it shows me that a specific achievement was won by 0.0% of players).
I'm an old player. Decades ago I played BG1 and BG2. I've been waiting for this game for 20 years... Thanks to the GoG team for ruining my game release of the year, maybe even the whole decade. Now, even if you fix the existing problems, it will still leave a bad taste.

I have done my research and checked both in the camp and in the gog client with the extras and so forth.
i have not received the DD yet, like so many others.

I can still play the game just fine, its just annoying to not have it available when we have been promised it.
I'm sure we'll get it eventually, just as I said, annoying.

Hope gog fixes it sooner rather than later, and that we get the updates at the same time as steam..

The link is the purest arse of gog :P