You have to set the GST_PLUGIN_PATH or GST_PLUGIN_SYSTEM_PATH environment variables
https://github.com/search?q=org%3Aflathub+"--env%3DGST_PLUGIN_"&type=code
https://gstreamer.freedesktop.org/documentation/gstreamer/gstregistry.html?gi-language=c
My application requires gst-plugin-rs gstreamer plugins
This will be included in Freedesktop SDK 24.08, coming out next month or so and GNOME 47 or 48 runtime.