Assuming you are running the node and using LND as an example in the lnd.conf file you can specify the TLS certificate used:
https://docs.lightning.engineering/lightning-network-tools/lnd/lnd.conf

Not perfect and you won't get everything but anything connecting to your node can then be read.
As a cheat, if you just want to see what is going on in general you can setup a bunch of nodes that just talk to each other and read all of their traffic.

-Dave