You can try Firefox from the official Mozilla server if you currently use a version from the repositories of your Linux distribution to see if it behaves differently.

• https://www.mozilla.org/en-US/firefox/all/#product-desktop-release

I think I'm using mozilla PPA for apt (to avoid the snap package)

David Moberg said

I think I'm using mozilla PPA for apt (to avoid the snap package)

What does Help and About Firefox show? See screenshot of Distro and Mozilla Firefox. X11 or Wayland? What happens on a different desktop? Do you have the same issue with Firefox in Troubleshoot Mode?