Hi,
Generally we run UDP streamin through gstreamer. Here are two posts for reference:
Jetson 4k Encoding -> Decoding Pipeline and latency - #11 by DaneLLL
Delay in video - #5 by DaneLLL
Our plugins are used for hardware encoding/decoding. For multicast, may see if it is supported in udpsink plugin. Suggest you may go to gstreamer forum. Users in the forum may have more experience and can share guidance.