There should be a config file in ~/.config/MangoHud (you can check more details in the GitHub page https://github.com/flightlessmango/MangoHud#hud-configuration).
By adding frametime=0 to the config file, you should be able to remove the frametime measurement from the FPS display.
Sorry for the late reply. I didn’t get notified of new messages.
I found these bug reports on Bugzilla:
At a quick glance these seem to be the same issue you noticed.
Based on some reports in Bugzilla, the missing option to open in app seems to be a few month old bug. A workaround that I’ve been using is to “Share” the link with the app you want. Assuming the app supports it in the first place.
It’s maintained on GitHub, so you might be able to manually install it or find a package for it in your package manager. At least on Arch you can install gnome-shell-extension-ddterm-git from the AUR.
I use ddterm, which is pretty much the only remaining drop-down terminal extension. https://extensions.gnome.org/extension/3780/ddterm/
I get the same errors about descriptor, but no mention of mlt or missing libraries.
I tried the flatpak version and that seems to be working.