With everyone’s catalytic converters being stolen, what is your recommendation to help deter theft? I’m not trying to spend an arm and a leg. I know nothing is foolproof, but really looking for deterrence.

Put the following in google and see what comes up:

site:toyota-4Runner.org/3rd-gen-t4rs/ converter protection

A loud alarm and a gun

A skid plate, covering the cat plus the pipe forward of the cat.
If you trace forward from the cat (49-state version, like my 97), the pipe soon rises up toward the manifold and is, at that point, out of reach for the sawzall artists.
I guess you'd have to get something like the RCI trans skid plate and add a side flap extension to it.

in the Arizona groups I was in before moving back to So Cal (but also 1 or 2 guys in our So Cal group) are welders either by trade or just pure hobby...they've made cages usually out of old rebar and then weld it around the cat.

I'm betting 9/10 times anyone who gets under your vehicle and sees that it isn't a 20 second job is just going to move onto the next vehicle....it doesn't take much to deter thieves seeing how they're looking for the quick/easy steals.

You can also just have them weld a length of rebar to the pipe itself, running the length of the cat. About a 3 ft section in total. That's exactly it, theives are looking for a return for their time and when they see a set of sockets and a sawzall isn't going to do the trick they move on to an easier target. That's why they target 4x4's in the first place as they are the easiest with all that ground clearance. Now if we were talking about a Prius, this would be a totally different story as those get hit pretty often out here and they are NOT easy to get to.

My local PD department does free catalytic converter etching and painting every year. I don't know if it deters thefts as there's enough bad actors in the recycling industry that might take an etched one anyway.