[camelreef]

What does this wpa_supplicant do? It does not scan for networks and "shortly" replaces the default route or something?

 It's used for the Wi-Fi connection and associated crypto. Sure, it can scan, and potentially mess-up the network connection (though that has been fixed a while ago). But the files are local, on an external USB3 HDD, access as a local filesystem, not Samba, and thus should be unaffected