I'm used to owning vehicles that have very active communities for buying/selling used aftermarket parts. With the 2020+ Defender being around for 4+ years, I thought it would be no problem finding/buying used parts. However, I'm not really seeing much in the Marketplace section of this forum (or others) and seeing if this is standard for our Defender or if I'm just looking at the wrong sites.

 

This is pretty normal; there aren't many official places where you can find accessories for L663 Defenders (or many modern JLR products) other than some facebook groups and ebay. The new ones don't have the same amount of aftermarket support that the older models do.