Do wire end ferrules have UL approval?

Yes.

According to UL Standards 486A and 486C, wire ferrules need to have UL approval.

FerrulesDirect is the only company in the U.S. that offers UL approved ferrules

See UL File #E326725.

This file can be viewed by clicking on the following link:

http://database.ul.com/cgi-bin/XYV/template/LISEXT/1FRAME/showpage.html?name=ZMVV2.E326725&ccnshorttitle=Wire+Connectors+and+Soldering+Lugs+-+Component&objid=1080000623&cfgid=1073741824&version=versionless&parent_id=1073810011&sequence=1