Hi @steeley 
I suspect the error is caused by an outdated entry in your config.toml file. Do you have a global config file located at ~/.streamlit/config.toml or a project config file at $CWD/.streamlit/config.toml , where $CWD is the folder you’re running Streamlit from?
If so, deleting the file will likely fix your issue. All config options related to s3 were removed in v1.4.0.
Best, 
Snehan