To enable libnice logging:
- Set NICE_DEBUG env var to "all" or one of these values
https://gitlab.freedesktop.org/libnice/libnice/-/blob/ae3eb16fd7d1237353bf64e899c612b8a63bca8a/agent/debug.c#L59
- Set G_MESSAGES_DEBUG env var to "all" or one of these values
https://gitlab.freedesktop.org/libnice/libnice/-/blob/ae3eb16fd7d1237353bf64e899c612b8a63bca8a/agent/debug.c#L67

E.g.
NICE_DEBUG=nice G_MESSAGES_DEBUG=libnice /path/to/janus/bin