Printing via the file->print menu in Jupyter lab is rather broken (and has been for a rather long time). To mention a few issues:
- equations are not rendered (as you have just discovered);
- images embedded in the notebook and referenced via html do not print (Attached image not exported if referenced from <img> tag · Issue #1057 · jupyter/nbconvert · GitHub)
- svg images do not print
- and surely more.
My advice is to simply ignore the print functionality from the file menu (that IMHO should be hidden from the user altogether until it can be fixed, because the many breakages make it just confusing). If you need a printout, use nbconvert to html and then open the html with a browser and print it.