I can wrap my mind around how to backup a seed phrase. And how to make it durable.

For lightning, as I understand it, you need a new backup each time you transact. And the backup data isn’t something you can write down…it’s too much. So the backup must be digital.

I also don’t grok how lightning handles bitcoin wallets. Does it have its own? I know LND uses seed phrases that are clever enough to encode “birthday” in the seed itself, so presumably it must have its own bitcoin wallet.