Viewer pane not rendering html/revealjs documents

I think this may relate to #11609 in the quarto-cli GitHub repo. I have noted (for a couple of rstudio releases now) that rendering a qmd presentation works fine, but the resulting html doesn't show on the presentation pane. I am on Linux (Ubuntu and PopOS, in different machines, but the problem remains). The file gets created and I can open it in my browser, but all the buttons are greyed out in the presentation pane.

Rendering a qmd document to pdf also works OK, except the resulting pdf doesn't show up automatically -- only when I hit the "refresh" button in the viewer pane, after which it shows up.

Not sure whether that's a Linux-specific problem? Or am I missing something obvious?

Thanks,
Gianluca