You can find a peel chain like this:

(1) Use a lightning explorer (e.g. 1ml.com) to find lightning nodes that frequently create both types of channels, public and unannounced channels, e.g. LSPs like Acinq and LNBig do both.

(2) Find one of the transactions where they open a public channel. This is easy to do because public channels are announced in LN gossip, including their funding transaction, so you can literally just grab it from gossip and look it up in a block explorer.

(3) The funding transaction is likely to have two outputs: a public channel and some change. Follow the change.

(4) The LSP is likely to use the same utxos for both types of channels -- they'll create channel A, keep the change, use A's change to fund channel B, keep the change, use B's change to fund channel C, etc., and occasionally add more on-chain funds when the change output gets too small.

(5) That's a peel chain, and it has an identifiable fingerprint. You can identify the change easily because it gets spent again pretty soon; whatever's not change in any of those transactions is a channel. The ones that are announced in LN gossip are public channels; the rest are unannounced channels.