I'm an MLT user via several open source NLE video editors (kdenlive).
It appears that MLT is unable to process a 10 bit LUT.
Prior to MLT 6.10 applying a 10 bit LUT like the DJI Mavic 2 Pro DLOG-M LUT resulted in blank output. After upgrading to MLT 6.10, the output is non-blank, but the LUT is not actually applied.
Perhaps there's a problem with DJI's LUT, but I suspect it's just a 10-bit vs 8-bit thing. Can anyone confirm, and weigh in on whether 10-bit support is in the pipeline? If so, the benefit would accrue to a lot of projects. I can supply luts and video samples.
You need to specific about which MLT filter you are using. There are several provided through FFmpeg libavfilter. There is no universal standard LUT file format, and I suppose lut3d does not support that LUT format.