My mom's iMac is having issues (it's booting to the "prohibited" circle with a slash), and needs the OS reinstalled. She'd been running El Capitan, and I'd like to reinstall the same since she has some apps that could be incompatible with a newer OS.
Her rural internet is abysmal (think dial-up speeds) and there is no way she'll finish a full download of an OS from her home, so I am intending to create a bootable install disk for her. But when I try to download the El Capitan installer it does not allow me to even begin the download since my computers are all 2018 systems running High Sierra.
Is there any way to download a copy of El Capitan from a High Sierra Mac?