At this time, Ledger is not compatible with Gaia. This is because Gaia uses an app private key* to encrypt and manage data. With Ledger, it’s not possible to access the private key so we are unable to support Gaia with Ledger.
*Note that Ledger is not supported with anything that uses an app private key. Please feel free to email email@example.com to report any other instances of this, and we will update our documentation.