I cannot admit that I’m trying to catch what are you about (if using PureOS GNOME) but still this might help you further:
Otherwise, if mentioned package deleted (apt somehow), you should be able to use Recovery Environment with Ethernet connection and go back with: sudo apt install xwayland.
And here is PureOS link to dependencies you are looking for: https://software.pureos.net/package/bin/amber/xwayland.