Both don't ship with their own Wayland compositor, but there are enough to choose from.
Xfce comes with a wayland session using labwc out of the box, but was also tested with Wayfire. The devs state you shouldn't hold your breath waiting for the native window manager xfwm to be ported into a Wayland compositor, since they don't know if/when it will be done. Almost all other Xfce components support Wayland now, while retaining X11 compatibility.
LXQt's newest stable release has full Wayland support, with 7 different Wayland compositors to choose from within a GUI settings menu: Labwc, KWin, Wayfire, Hyprland, Sway, River and Niri
https://xfce.org/about/news/?post=1734220800
https://lxqt-project.org/release/2024/11/05/release-lxqt-2-1-0/
A compositor is normally a component in a DE, not a DE on its own. For it to be a DE in my book the "standalone" installation needs to, at minimum, provide: a launcher to execute apps, a toolbar/statusbar, and maybe a terminal emulator (or at least call some generic wrapper to automatically hook into one, something like xdg-terminal-exec).
I mean.. openbox is used in X11 desktop environments like LXDE.. I don't see why labwc (essentially wayland's openbox) should be treated like it cannot be a component of one.
And river has almost as a mission statement to become more of a framework than a DE on its own.. they even have the goal in the long term to remove things from it and instead expose more to the commands/API to make it more modular.. it's definitely not something intended to work standalone and they expect people to develop third party layout generator programs.
Maybe sway is the one in that list that might be the most "standalone", since it does have swaybar built-in.. but the default configuration still expects you to provide at least something like dmenu to use as launcher, as well as making sure you have your terminal, etc, since it does not list them as specific dependencies of the sway package, so officially they aren't really part of sway as if it were a DE suite.