So I'm a dumbass and apparently RaspiBlitz already does it, but yeah I don't see why it's not used more considering it's more suited for peer-to-peer connections.
Discussion
Okay, maybe I shouldn't comment on things when I'm at work. I'm checking their docs and it looks like it's not I2P. But ip2tor.
The change log on GitHub shows support for i2p for Bitcoin Core. Not sure how to apply it to LN (ie CLN or LND).
The way I've been playing with it on Lightning is to just set up a normal server tunnel and make it accessible on the ports that LN normally listens on. I've been playing with that on test net.
It's not default supported like the Tor network, so it's a bit tricky to test that it's actually working and I don't think anyone is actually using I2P on lightning. (Due to the lack of default support.)
I know way too little about I2P