Avalanche does not support migrating from Lightroom CC directly because CC has a specific cataloging structure that Avalanche does not understand.
However, since migrating from CC to, say, Luminar, requires all photos to be stored locally, here is how you can proceed:
- Start by syncing Lightroom CC with a Lightroom Classic catalog (see Adobe's instructions). If you want to specify where the synced images will be stored, you need to select the specific location from the Lightroom Classic Preferences screen (see Adobe's instructions).
- Once syncing is finished, you will have a Lightroom Classic catalog that is ready to be migrated
- In Avalanche, you probably want to uncheck the "Copy referenced Master files" options in order to not create yet another copy of your masters.

Migration from a synchronized catalog requires Avalanche for Luminar 1.0.1 or above, or Avalanche Unlimited 1.0.1 or above