Doing ssh through port 80 or 53 or 443 is immediately flagged.
I understand port 443 is always opened but nowadays you can’t just run ssh traffic on 443 without it being detected as not being https
Flagged by who? The Internet Police? This comment is absurd.
Naive. There's not much that prevents you from running ssh over https. Not even traffic patterns will give you up in the age of ubiquitous websockets and/or http2 streams.