You might have to wait until it's implemented, in the next image update, but at the moment Kodi 18.9 is still working, for me.
A lot of images were still using older versions, of KODI, than Leia, the last time I checked, which admittedly was some time ago, so it might take a while, before we get the Matrix version.
It is installed, as a plugin, when you load an image, so you generally don't have it installed, with the image, but select it, during installation, and if not you can then download it, from the plugin menu, you can also go into the plugins downloads, and see.