The command line help for deploy implies that streamlit and dash are supported on shinyapps.io:

streamlit      Deploy a Streamlit Application to Posit Connect [v1.8.4+],
                 Posit Cloud, or shinyapps.io.
dash       Deploy a Dash Application to Posit Connect [v1.8.2+], Posit
                 Cloud, or shinyapps.io.

but trying to deploy a streamlit app to shinyapps.io doesn't work (at least on the free tier I'm on) and there's no documentation I can find anywhere that suggests shinyapps.io supports streamlit or dash.