Syncing a Bitcoin node over Tor is 100% feasible and many of us have done it, some of us for years now.

I see no reason a lightning node couldn't be served as a hidden service, but I haven't tried to run a lightning node yet.

Having said that, I have no objection to someone writing a guide, or better yet automation (ansible playbook, scripts, etc.) to set up a lightning node over I2P, gnunet, Veilid, or any other mixnet/overlay neteork.