Most forest service campgrounds with outhouses/SVTs only don't mind if you dump them out in the pit. On the whole, it is not a common occurrence and it is not a significant drain on the resource. Check with your forest and/or camphost first tho.
If you do, Please do so nicely.. I have to clean those things all summer. I always know when a not so conscientious camper has dump thier potti. Not fun.
I have fulltimed for near two years with just a porta potti. As a camphost, I usually have a sewer pod or tank at my site..it goes in there. I also dump into a blue tote/blue boy and haul it to the dump station when I am boondocking
on BLM land in the winter.
If you are in a park with "Flushies" use them for most of your "Duties" and you can also dump the potti in the toilet if they allow. Again.. be clean about it.