1 1/2" hole was more than likely and old style deadbolt. Most install in 2 1/8" hole now, FWIW.
Anyway, you can repair with a same diameter and thickness plug, but if you have access to a router and a few tools it might be easier to rout a rabbet around perimeter of hole and glue in a 1/2" thick cap plug...one on each side of door.
I can think of a few more, but I don't know if they'd be considered "proper", since I'm slightly off-kilter anyway.
If it's the door and not the jamb that threads are stripped, a longer screw might work. Don't bother with wood filler if you're looking to restore thread-ability. Just not designed to do that kind of thing. Epoxy and dowel is your best bet.