Did you use a new SSD or something? You should be able to just plug the SSD into the new RPI and have everything work. All the data is stored on there, not the SD Card.
Channel backup file is typically used to recover funds from channels onchain after a serious failure/corruption of lnd data.
Does this sound like the steps you took? https://docs.lightning.engineering/lightning-network-tools/lnd/disaster-recovery
If so, you have force-closed all your channels.