Pulling my hair out figuring out why SQLAlchemy was giving me access denied with a legitimate account. Turned out "mysql+pymysql" failed with access denied, but "mysql+sqlconnector" succeeded. I suspect it had something to do with that "caching_sha2_password" thing.
Could not figure out why my Posit Connect application would not run with the error "Application is of type dash which is not callable". After a couple of hours, I realized that I was deploying with the "api" deployment rather than the "dash".