Most old Chromebooks can be converted to Linux using Mr ChromeBox's excellent firmware upgrade script found here. It requires removing a hardware or software Write Protect feature that involves opening the back of the computer and shorting a jumper, removing a screw or momentarily disconnecting the battery.
The Acer C710 Chromebook is one of those older machines that is particularly well suited as it uses a regular 2.5" SATA HDD instead of the paltry 16GB eMMC devices found in many Chromebooks. While it is generally well built, the connector for the HDD to the motherboard can be finicky and can come loose but is easily remedied with the help of some hot glue. I recommend swapping in an SSD drive to improve performance.
Disabling the write protect involves stuffing some aluminium foil into the jumper socket to short out the pins as shown here.
Once that's done you need to download a newer version of ChromeOS as the last supported version (65.xxx.xxx) lacks a valid CA certificate used by the Firmware Upgrade script. You can find it here.
Hope this helps anyone who has thought of upgrading their old Acer C710.