2 concrete lines with references to 2.4 (https://docs.gimp.org/en/gimp-scripting.html#gimp-plugins-install)
-
~/gimp-2.4/plugins
->~/.config/GIMP/2.10/plug-ins
?
Quoting section 1.3.1. Linux / Unix-sytem like systems
of https://docs.gimp.org/en/gimp-scripting.html#gimp-plugins-install
For a simple one-file plugin, call it borker.c, installing it is just a matter of running the command gimptool-2.0 --install borker.c. This command compiles the plugin and installs it in your personal plugin directory, ~/gimp-2.4/plugins unless you have changed it. This will cause it to be loaded automatically the next time you start GIMP. You don't need to be root to do these things; in fact, you shouldn't be. If the plugin fails to compile, well, be creative.
With 2.10.30 I have installed, I think ~/gimp-2.4/plugins
should be replaced by ~/.config/GIMP/2.10/plug-ins
.
-
Xtns/Plugins
->Help/Plug-in Browser
?
In a similar manner, I think Xtns/Plugins
should be replaced by Help/Plug-in Browser
.
The menu path is determined by the plugin itself, so to answer this you need to either look at the documentation for the plugin (if there is any), or launch the Plugin Description dialog (from Xtns/Plugins Details) search the plug-in by its name and look of the Tree view tab.