Ignoramus27780 wrote:

I bought a forklift today. It is a 30,000 lbs forklift with a diesel
engine.

To make it more palatable indoors, I would like to find some way to
scrub/purify exhaust gases. Can I add something, like a catalytic
converter, DEF box, afterburner, or some such?

A DPF would trap soot, however they also need to be regenerated
regularly so you can't just add one to an exhaust system not designed
for them.