Here's an example of Asobo's LODs. I use an example from MSFS 2020, but the object is essentially the same for MSFS 2024:
Gen_Hangar01 LOD0
There are some asset parts, like lights, doors, aircon units... Nice details.
LOD1:
In LOD1, they dropped all the little details.
LOD2:
In LOD2 (the final LOD they used), they use only the basic blockout of the model, and use just colors for the materials.
The xml will look about like this:
XML:
<?xml version="1.0" encoding="utf-8"?>
<ModelInfo guid="{65b40360-eadb-4927-82cb-a5af526f5377}" version="1.1">
<LODS>
<LOD minSize="15" ModelFile="Gen_Hangar01_LOD0.gltf"/>
<LOD minSize="8" ModelFile="Gen_Hangar01_LOD1.gltf"/>
<LOD minSize="0" ModelFile="Gen_Hangar01_LOD2.gltf"/>
</LODS>
</ModelInfo>
And note, with MSFS 2024, the sim decides the actual minsize regardless of what you write. So there it is for some of Asobo, and Microsoft's models.
You could almost work backwards when making a model. Block out the lowest LOD2 with colors, then from that add mesh and material for the next LOD1, then add asset details for the LOD0. This example used LOD 0-2, but you could use more if needed... perhaps LOD0-4 for a total of 5 LODs.
ModelconverterX is great for making simplified mesh for LODs, but the lowest blockout would probably be best handmade. And the LOD1 (elimination of detailed assets) could also be hand edited from your LOD0. Leaving the Mid-LODs to be simplified by decimation (like MCX does), and perhaps elimination or baked combination of textures and materials.