Stratum on its own is not secured and you can easily reconstruct the TCP going through from miner to pool server.

That being said the Stratum V2 being pushed by Braiins would be encrypted while in transit but it is not a standard protocol as yet and doesn't look to be anytime soon.

If you are looking at finding out shares being sent back to pool and the share diff etc, these can mostly be found on the miner's dashboard or via API and might be easier than sniffing and reconstructing packets.