Local BMW shop quoted $2600. Symptoms, you can hear rattling when idling, get worse when you take off. When you max adjustment on clutch, gets better. I think the previous owned replace clutch and did it incorrectly. Any local gearheads in Dallas want to take on this challenge, above my skill sets.
Welcome to the forum Jim. the LT is often called a box of rocks and you are generally told to not listen too closely or you will lose your mind thinking it is falling apart which is another issue entirely. Here is a summary of the things that can make noise that are generally not life threatening. The clutch will generally not make noise on its own especially with the clutch out.
Diagnosing a sound remotely is often difficult. First, when you begin pulling in the clutch, does the rattling stop? If it does, then the noise is likely the clutch pushrod rattling with no load on it. It is a Hydraulic clutch so there is no adjustment to speak of. If you adjust the stop screw too tight in the handle, that can block the fluid return hole and lead to other issues. The pushrod has a piece of felt around it to prevent it from rattling so if that is worn or was removed, it can make noise. To replace the felt, removal of the final drive and swing arm are necessary to reach the clutch slave cylinder where the rod can be removed and the felt replaced. Some early models did not have this felt but I think a 2003 should have been equipped from the factory
Other possible rattling is caused by gear lash in the alternator drive. Turn on everything you can, lights, heaters, high beam and see if it gets better with a higher load on the alternator. Not much you can do about that one but if that helps, you at least know where the noise is coming from.
The cam chain can make noise( rattle) if the tensioner is not doing its job well or if the guides are severely worn but most that have in excess of 100K still see no issue there with worn guides.
Lastly, there is a less likely possibility of the output shaft in the engine making noise. A much bigger job to try and silence that but it won't cause any damage.
If you are in a state that doesn't require a helmet, try wearing one. That will quiet the engine and also protect your head.