I have door-off approval EOs for all my PA28s for aerial photography , one archer also has approval to fly with the baggage door removed. There are a few airspeed and bank angle limitations but that’s all. I’ve dropped skydivers from PA28, Islanders and C182s with various configurations some with roller doors some with door removed for the whole flight. Not sure why it’s a big deal in a non pressurised light aircraft?
Edited to add I would never get in an aircraft like the one described in the post above where it has a hinged canopy, apart from it coming open and blowung off, there’s been people trapped in these things if they end up landing on the roof.