@M2m got me curious about playing around with .g files myself, with his converters and various scripts. I remembered Simon from the LU community had made a .g importer script for Unity some time back, so I got it from him, and tidied it up + expanded on it some more (added support for .g1/.g2/etc files, and UV coordinates), then rigged it up to some obj exporting code. Mostly just for the fun of it, and also cause I hadn't done any binary file reading before, and it seemed like a good chance to see how it worked.
Here's the result, a standalone program that can convert LDD .g bricks to OBJ:
https://github.com/Terrev/G-to-OBJ/releases
On my machine, it converts all 4186 bricks in the LDD library in 1 minute, 2 seconds. I have a solid state drive; it will probably be a bit slower on a mechanical hard drive but still fairly fast.
I was thinking of rendering out icons of bricks too, but couldn't think of a practical use for myself, and anybody who'd want that could do it themselves with their program of choice.
If you use this on bricks from LDD (as opposed to, say, .g files from LU), be aware you should be using the contents of db.lif in AppData, NOT Assets.lif in Program Files: https://www.rockraidersunited.com/topic/7899-ldd-updatingpatching/
To extract LIF files, I recommend: https://github.com/JrMasterModelBuilder/LIF-Extractor/releases