Ephemeral in thoery...except that most LN node software saves and stores transaction info by default, and you also don't control what info other nodes save. Peter Todd did a talk on this problem a few months ago showing how his node still had transactions he made over a year ago. Onion layers aren't a magic barrier. Tor has a long list of attacks that can reduce or completely deanonymize you. Now consider that even if you use LN in a private way (vast majority do not) less than 1% of lightning nodes hold over 99% of total liquidity...

GitHub

GitHub - Attacks-on-Tor/Attacks-on-Tor: Thirteen Years of Tor Attacks

Thirteen Years of Tor Attacks. Contribute to Attacks-on-Tor/Attacks-on-Tor development by creating an account on GitHub.