Where to download Quartus linux 15.1 for web/standard version

15.1 is no longer available for download.

13.0sp1 and 13.1 are available specifically to support some older architectures.

17.0 and later are available for newer devices.

Downloads here: https://www.intel.com/content/www/us/en/collections/products/fpga/software/downloads.html?edition=lite&platform=windows&s=Newest