According to link below, Quartus 8 is still available to be downloaded. This version of Quartus II software will no longer be available after 6/26/2020. This version does not include the latest functional and security updates and will not be supported. All versions are provided as is. Intel recommends that users of this version uninstall and discontinue use as soon as possible. Besides, Win 10 does not support for Quartus 8. Refer to link below for details.