Currently it seems the downloads only include versions 5 (remastered) and classic. Any way to play the next gen version? (or maybe it is somehow avalible through gog galaxy?

In the GOG launcher, after clicking on the installed The Witcher 3, click on “MORE -> Settings” (where you can choose to install online versions 5.00b/4.04b/4.04a_REDkit/4.04a_Launcher/4.04a).

The idea is to have it available for download on Goodies.

And, suddenly, the NEXT GEN version appeared

It is 2026, and GOG is still unable to provide older versions of games, they should make all updates available.

This is a massive downgrade compared to Steam, which provides access to every version since day one.

You can pretty much download The Witcher 3 exactly as it was released on day one on Steam, meanwhile on GoG oldest version we have is 1.32.

Version 5.00c was released today, and version 4.04a has disappeared from “MORE -> Settings” (meaning that the last 5 versions are visible in that tab).
So I assume the files are probably still stored on the servers, even if they’re no longer visible in “MORE -> Settings/Backups & goodies”.
I haven’t checked this myself, since I don’t need to, and I don’t really feel like checking just for the sake of it. However, perhaps https://www.gog.com/forum/general/gogrepopy_python_script_for_regularly_backing_up_your_purchased_gog_collection_for_full_offline_e/post1 or https://www.gog.com/forum/general/gogg_downloader_update_it_has_a_gui_now/post1 can see all the files that are needed, assuming they are still on the servers.

They cannot because it uses the same backend as GoG Galaxy, so unless GoG exposes the files to the API is not happening.

Still think this is a major downgrade compared to Steam, that supplies us a backend to download all game versions.

In Galaxy, click on The Witcher 3, then, on the game page, click on the 'more' button at the top (the one on the right that looks like two little lines with little circles).

Go to 'Manage installation >'

Click on 'Configure'

Under the 'Installation' tab, look for 'Beta channels'

Click on the drop-down menu and select your preferred version.

Now click on 'OK' at the bottom, and the game will begin to update to the version you selected.

Now an intermediate "Next-gen" (4.x) edition has been added, but in different file download chunks (each equivalent to about a 20gb portion, more or less a blu-ray). It's in the goodies for the offline installer (and in Galaxy, as it always has been since 4.x counted as a rollback version for 5.x)