nice plugin unavailable in GStreamer 1.18.5
Managed to make that sample with modification to use videotestsrc to work on Ubuntu 20.04.3 LTS VM with GStreamer 1.16.2 after building & installing latest libnice. It works only with FF on the same VM, Chrome fails to connect after errors in ICE negotiations, same for any browser trying to connect outside of VM.
So I decided to give GStreamer 1.18.5 on Ubuntu 21.10 VM a try to see how webrtcbin & libnice work there...
Build & installed latest libnice and discovered that GStreamer 1.18.5 doesn't recognize nice plugin, despite it being in the correct place and gst-inspect-1.0 sees it when directed to it:
gst-inspect-1.0 /usr/local/lib/x86_64-linux-gnu/gstreamer-1.0/libgstnice.so Plugin Details: Name nice Description Interactive UDP connectivity establishment Filename /usr/local/lib/x86_64-linux-gnu/gstreamer-1.0/libgstnice.so Version 0.1.18.1 License LGPL Source module libnice Binary package libnice Origin URL https://nice.freedesktop.org/
nicesrc: ICE source nicesink: ICE sink
2 features: +-- 2 elements
Tried to delete ~/.cache/gstreamer-1.0 folder to force plugin cache rebuild - same result, nice plugin is still unavailable to GStreamer.