Compressed 3d lut are now available for lut3d module on dt master.
If you build dt yourself make sure you have the GMIC library at a version above 2.7.
For windows GMIC 2.8 is available on MSYS2.
$ pacman -S mingw-w64-x86_64-gmic
For linux I’ve found it here for Ubuntu and Debian.
I don’t know anything about Mac OS. Hopefully somebody will help us on this.
You can download the up-to-date GMIC compressed lut file gmic_clut.gmz.
If you need to manipulate 3D lut file, GMIC can help you. You may find useful some GMIC commands above in this thread and at the end of this post on darktable site.
For performance reason the compressed luts are cached. Cache folder and cache files are shared with GMIC.
As somebody already said, enjoy.