I have a rmd flexdashboard, and wonder if it is possible to launch using python.
Not totally sure I follow what you mean by "launch using python"?
I see most Rmd flexdashboards deployed to shinyapps.io (especially when there's a Shiny component) Posit Connect, or something like github pages (Deploying flexdashboard on Github Pages) or rpubs for static docs.
If you mean execute python in a flexdashboard like doc, Quarto is basically next-gen R Markdown (quarto.org), and will very soon start supporting flexdashboard like formats. It supports R, Python, Observable, and other languages. It's arguably getting close to flexdashboard today if you want to dive into your Component Layout options with Quarto.
And then of course there is Shiny for Python, Shiny for Python