A small reminder:
Once features land in Mir they are available from the “Latest Integration Build” PPA and from “edge” version of the egmde snap:
snap install --classic --edge egmde
egmde --wayland-extensions wl_shell:xdg_wm_base:zwlr_layer_shell_v1:zxdg_output_manager_v1:zxdg_shell_v6