Did jupyterlab 4 drop support for restructured text?

When I open my Sphinx docs .rst files in Jupyter Lab 3, there is rst syntax highlighting.
When I open them in Jupytyer Lab 4, the syntax highlighting isn’t there.

Did Jupyter Lab 4 drop support for .rst files or is there something wrong with my setup?

the rst mode was not ported to codemirror 6:

So someone would have to build a new parser for it.