You're right, there is no clear answer out there. I shoot steel out of my old guns sparingly, and only if they are choked Modified or less. I suspect most of the damaged barrel talk is hype, and after a few cases I've seen no damage in my most used Model 12, but I'm still cautious, just in case. Steel patterns tighter than lead, and most would probably agree that on old Full choke should be retired for the purposes of steel shells.
What type of gun/choke are you considering? If it's an old Mossberg or Sears or Higgins you could shoot plutonium through it, what's the worst that could happen? If you're talking about a pigeon grade A5 with a full choke, I'd get a new gun.