ok, sorry if I use the wrong terminology, however I also realise that the link for PureOS does not work, its currently pointing to:
which looks like an older update, while the latest under
is 2018-01-06, and you have both the checksum and ISO you can download.
I downloaded the ISO file and checked the sha256sum signature,
$ sha256sum Downloads/pureos-8.0-live-amd64.hybrid.iso
and it matches with the value in the checksum file.
PS: pursim has fixed the download linked