Thanks all, for your advice.

The more I'm asking around about this, the more it's a "grandfather"
issue. The bath can be left as is, and I can sell it as is. Ditto if it
was a non-conforming bedroom that WAS conforming at time of
construction.

But if I choose to replace any of the bathroom fixtures I may be forced
to upgrade the plumbing and install P-traps. This means breaking up
concrete etc. That is, of course, if I decide to pull permits. But
permit or not, a sewer-stinky remodeled bathroom isn't what I'm looking
for.

*sigh* I didn't know squat about bathroom code until I got all excited
after the offer was approved and I started researching my fun little
bathroom project.