https://github.com/GodotVR/godot_arcore
While this plugin is in development, you'll need to check-out the Godot Engine ARCore branch in PR #41026 and update the GODOT_HEADERS_DIR variable in the CMakeLists.txt file to point to its godot/modules/gdnative/include directory.
If I'm reading that right then you probably shouldn't expect an official pre-built binary before it's out of active development. If they even have plans for pre-built binaries, might be they consider there to be too many varying CPU architectures out there to viably cover them perhaps. I simply do not know.
edit: if you really want to know what their plans are on this you should probably open an issue on the above linked tracker and ask there. Though I can try and ping @BastiaanOlij here and see if perhaps they can reply here too.
