Zgemma H7S is a monster machine and by far the best of the lot available to the general public. It's a fabulous combination of HW, Linux kernel, drivers and Enigma2, plus additional SW (plugins/addons) etc. etc.
Amongst other things, H7S boasts a large, 4GB eMMC NAND Flash, partitioned in 4 major partitions (if we are speaking in "everyday language"... it's actually partitioned in 8 partitions but OK...)!
I.e. one can install 4 different images natively, without any additional "multiboot" plugin/addon and there is no need to install those images on a USB stick, provided an image has that part of the SW included, of course.
Here is how to do that.
PurE2:
0) We shall, of course, presume you already installed PurE2 on the first/default partition, in a usual manner anyone can find and follow, including on this and other similar forums...
1) Download other compatible images you want to try (OpenATV, OpenHDF, OpenSPA etc.) to your PC, for instance, and do NOT unzip/decompress them!
2) Have a suitable USB memory stick formatted in FAT32, then send an image you want to install on your H7S, to the USB stick, zipped as you downloaded it. Plug it into H7S.
3) MENU > pMANAGER > SW MANAGER > FLASH ON THE FLY (to get to the flashing menu)
3a) yellow button (to choose an H7S partition for installation of the new image) - be careful not to install the new image over the existing, already installed image on the current partition - choose a different partition (unless you want to overwrite the old image, of course)
3b) blue button (local file installation, as opposed to online installation)
3c) choose the device from which to install the unzipped image (find the image you want to flash)
3d) green button (to start installing the chosen image from the USB stick) - installation starts...
4) Wait... when successful, press OK to reboot H7S.