It seems that the action “Open in Terminal” is gone from the context-menu as well as the “main” hamburger menu (the left hamburger menu next to the address bar, NOT the hamburger menu on the bar’s right) in the current nightly build of the app “Files” from FlatHub.
Is this a deliberate design choice or is this due to some integration/sandbox issues with FlatPak?
The “Open in Terminal” menu entry is not provided by Nautilus itself. Instead it is provided by a Nautilus extension included in gnome-terminal or gnome-console, neither of which are part of the Flatpak.
Indeed, the flatpak’d app cannot pick the extensions installed in the system.
I wish for the “Open in Terminal” action to be provided by the application itself, but we need to figure out a good way to know what the user’s preferred terminal application is.