There is a June thread that has good info on the LMT…
In short, LMTs are a Linear-In to Linear-Out conversion to an ACES color space file.
A general 3DLUT from another place can be converted if you know what the colorspace_in and _out
are, and what transfer function and quantization are being used in that LUT. But that process can be tricky.
If the LUT has the final look baked into it, then you would want to use a path that takes the output
of that LUT for a particular device and invert it through an InvODT/InvRRT, to get rid of both the RRT and ODT tone curves. This will limit the dynamic range of the file to whatever device the 3DLUT was made for.
To go further, I would have to look into the .ari format a bit more, so perhaps someone else can jump in.
Jim