This appears to be legit. I got the email about free Lumens, but I don't have a Stellar key signed by my private key. Granted, I haven't signed into my account

This appears to be legit. I got the email about free Lumens, but I don't have a Stellar key signed by my private key. Granted, I haven't signed into my account from any of Keybase's mobile apps, but it seems unlikely that they would backdoor _only_ the mobile apps.