Eugen, that confused the heck out of me too, I thought suddenly I had to download 2x the ISO’s!
However, if you read some way further down the download page, you’ll see an explanation of the ISO’s in question. The QU DVD ISO’s are apparently a “Quarterly Update” where if you look each 3 months, the newest ones have all the patches/fixes/updates from the GA/GM release up until THAT QUARTER. Or something like that. Anyway, here’s the text from that page.
[QUOTE]Media Selection
For both, the Installation Medium as well as the Packages Medium, two flavours exist:
The first, containing’GM’ in the filename consists of the package set as shipped at first customer shipment date.
The second, identified by a ‘QU’ followed by a number in the filename, consists of the packages shipped at first customer ship, but all packages where maintenance updates have been released since then have been updated to the latest maintenance update. Quarterly updated media are refreshed every 3 months.
You only need either the ‘GM’ or the ‘QU’ media, not both. Which to choose, the GM or the QU version depends on your needs and preferences. If you have newer hardware, the QU version might be the better choice. The installation procedure is identical for both flavours.
For both flavours it is recommended to install the latest updates released since creating the images.
Both, the installer medium and the packages medium are the same for all SLE products and only need to be downloaded once.
SUSE Linux Enterprise 15 SP1 is available for the following architectures. Images for a specific architecture can be identified by the respective acronym in the filenames:
Files with “x86_64” in the name are for the AMD64 and Intel* 64 platforms.
Files with “s390x” in the name are for IBM* z System or LinuxONE.
Files with “ppc64le” in the name are for the IBM* Power LE platform.
Files with “aarch64” in the name are for the Arm* 64 platform.
For each architecture and media flavour two images are available:
DVD1 Required for the installation
DVD2 Source code, only required to rebuild applications on the installer or packages medium.[/QUOTE]