I have Macbook Air 2013-mid which has only Ubuntu 16.04 and reFind bootloader. Now, however, I Would like get OSX back to the whole disk. I find only updates of specific OS Xs here but not whole ISO file, which you can boot for the install. I have had licences of El Capitan on my Apple store but cannot login now to any Apple store.
I started the Internet recovery mode. It asks me wifi password. I gave it but it stays now in the mode where the Earth and you can still change the network settings. I have also Ethernet connection with USB connector to the device but it does not want to use it. Eventually, it gives the warning sign and the text
Hardware: Macbook Air 2013-mid
OS: Ubuntu 16.04 64 bit only at the moment