On gimp-forum.net:
https://www.gimp-forum.net/Thread-Conve ... 2#pid43522
user iiey has provided a link to a nikplugin.py plugin for GIMP 3 for image processing with external Nik Collection programs:
https://github.com/iiey/nikGimp

In menu:
Filters ➤ NikCollection

Thank you MareroQ for sharing this.

Thanks to iiey we now have an easy way to create image processing plugins using other external programs.

On 27/03/2025, iiey released a new version that displays a message on how to deal with the error reported by Zbyma72age in the HDR Efex Pro 2.exe file.

iiey released version 3.0.5 which fixed the HDR Efex Pro 2 issue. You should check in Settings though if the output format is set to jpg (because mine defaulted to tiff - and then it doesn't work).
New page:
https://iiey.github.io/nikgimp/



However, the plug-in does not work as described by Zbyma72age (because for it to work properly you need to open several photos from the HDR Efex Pro 2 menu).



what opens the window:

Some work very fast.
In ver.3.1.0 iiey solved the problem of loading multiple selected layers

Can't get the Nik collection for gimp 3 to show in my gimp. I have it in 2.10.38 and need it in 3 before I bite the bullet and change over from 2.10 to 3 completely.
I have the new updated py plugin for gimp 3 and have put it in the Plugin-ins in two folders as the plugin suggests.
Google>Nik Collection>py plugin
I restarted my computer then gimp and it still doesn't show - as greyed out even

If you are very patient, we will handle this problem.
1. Remove your version of nikplugin and install from the attachment (ver.3.1.0).
2. If it is still not registered in the menu, show a screenshot of the plugin location (so that the full path from C:\ to ....nikplugin\nikplugin.py is visible).

Edit:
Probably better - you wrote directly to the plugin author on gimp-forum.net. (I noticed your new post there). I won't interfere anymore (but you've stirred things up a bit).

When i installed it i had to remove the word Google from the directory the py plugin looks for the installed program Nik Collection because mine was installed in c:/Program Files/Nik Collection not
c:/Program Files/Google/Nik Collection.

Maybe check for that first.

Finally! I downloaded the file you attached and I have finally got it on my computer in Gimp 3.

Thankyou