I was using the Kumo browser from Flathub until a few months ago when it stopped launching. I saw that another user had reported the bug, which seems to be related to Mesa: Crash on launch on Librem 5 · Issue #115 · catacombing/kumo · GitHub
I assumed an update from either Kumo or Purism would eventually fix the issue but no such luck. I have seen the same problem on a couple of other Flatpak apps, although I don’t remember which ones specifically (games I think?). The problem persists whether forcing X11 or Wayland via Flatseal. Anyone else come across this or know what might be causing it? See the linked GitHub issue for error details.