How Do I enable client plugins in my server?

I added the "# This allows players to use scripthook-based plugins such as the legacy Lambda Menu.

Set this to 1 to allow scripthook. Do note that this does not guarantee players won’t be able to use external plugins.

sv_scriptHookAllowed 1" line to my server.cfg because the line wasn’t there already, and it still does not work. Any solutions?

did you figure it out?

Main thing you need to know is that not all plugins will work even with scripthook being enabled on the server (depending on how old they are and what methods are in use); you are considerably better off looking for server resources that do what you want. A resource can do pretty much everything any client-side menu can do, and a lot more.