Just bought an XDM Elite OSP. I would prefer to have a non-threaded standard 4.5" barrel. Does SA sell barrels separately?
I know some old XDM kits came with both barrels.

If aftermarket is the only option, are XDM and Elite model barrels interchangeable?

I am not sure about the new models, but I bought an early model XDm (still have it, love it) and i took it apart and hid the pieces as i was between homes, anyway, when I went to put everything back together I couldn’t find the barrel.  I called spring field to see if I could just buy a new barrel. Nope, no can do johnny. The barrels are individually fitted to the slide, so no interchangeable barrels or slides on XDm pistols as far as I know.

Maybe someone else with more recent and direct knowledge will chime in.

Edit to add i did eventually find my barrel

I can think of many places to hide a pistol assembled without having to part it out lol. But i'm not one to judge, I've put my carry gun a couple times in a drawer
instead of my normal spot and taken way too long to find it again.

Searching the interwebz it looks like SA barrels are not available, looks like it's KKM, Bar-Sto, or Springer Precision which are also made by Bar-Sto