I have been using the version from here https://sourceforge.net/p/supertuxkart/code/HEAD/tree/media/trunk/blender_25/
which seems to be what this was based on and I would like to know what you mean by this
not kept up to date with more recent versions - these are known to break the models' orientation and are thus not usable.
The current version seems to work pretty much the same as this other than it produces a slightly smaller binary, I see no visible difference in-game.
I would possibly use this if you did
keep it up to date as the texture unlink option is undeniably handy when making models for minetest.
Unfortunately, it seems that there is a problem with the b3d format when it comes to bone attachment, attached objects appear to switch sides and direction when the model is animated. See my latest findings on #2813
I currently have no idea what causes this but I guess it has to be either Irrlicht, minetest, the exporter(s) or the model itself. I have tested several revisions of the exporter and they all seem to exhibit the same behaviour.