your channel "backup" is going to force close all of your channels. you won't have anything on lightning once it's done syncing. it will all be onchain eventually. it takes a while.
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Oh dang. That sucks. Didn't realize that's what would happen. Thanks for the reply Derek!
you're welcome. yeah, it's not really a channel backup. that's confusing, huh? it's more of a funds recovery in case of disaster. a way to get your funds out of Lightning and back on-chain.
you CAN migrate all of your channels from one node device to another. i just did all of this actually a couple weeks ago. i migrated from umbrel to another device. you need to go in via command line and backup your LND directory, mainly your channels.db and wallet.db files.