I wondered about that. Back when my Air was still running macOS I setup netatalk on a linux server so I could point Time Machine there. But every few weeks I go

I wondered about that. Back when my Air was still running macOS I setup netatalk on a linux server so I could point Time Machine there. But every few weeks I got that message and had to repair my backup. I always assumed it was some issue with netatalk or my configuration. Eventually I gave up and used an external drive.