I just tried four times to install the latest version of OSMC to the HDD of my ATV1. I used the OSMC Installer running Linux. Both selectable versions in the installer (the USB and the HDD one) end up installing OSMC to the USB drive instead of the HDD (so there’s no “Please remove USB drive etc.”). I tried two different USB flash drives, which both had no problems installing the previous version correctly before.
I guess something is wrong with the download mirrors, is it?