xsane is the same. The xsane binary, which can run on its own, installs in /usr/bin and puts a link into /usr/lib/gimp/2.0/plug-ins/
I also have a Gimp appimage which goes nowhere near /usr/lib/gimp/2.0/plug-ins/ so I add my own link into the appimage plugins folder.
The OP is not too certain about creating a hard link. It is efficient but not vital. You can copy the whole xsane binary to the Gimp user plugins folder. Wonder if OP is using a flatpak ?
I also have a Gimp appimage which goes nowhere near /usr/lib/gimp/2.0/plug-ins/ so I add my own link into the appimage plugins folder.
The OP is not too certain about creating a hard link. It is efficient but not vital. You can copy the whole xsane binary to the Gimp user plugins folder. Wonder if OP is using a flatpak ?