The Fedora 33 Scientific page, https://labs.fedoraproject.org/scientific/download/index.html when the download link is clicked bringing the user here: https://labs.fedoraproject.org/scientific/download/scientific-download-splash?file=https://download.fedoraproject.org/pub/alt/releases/33/Labs/x86_64/iso/Fedora-Scientific_KDE-Live-x86_64-33-1.2.iso. The link at the bottom of the page for the link to the complete installation guide, gives a 404 error.

Additionally, when the .ISO is downloaded, and one attempts to use the checksum file after clicing "Verify 64bit!" the checksum file has no signature giving an error

gpg: no valid OpenPGP data found.
gpg: verify files failed: Unknown system error

A user over on the ask.fedoraproject found this: https://getfedora.org/static/checksums/Fedora-Workstation-33-1.2-x86_64-CHECKSUM
but while it gives a good signature, it also warns that the key is not certified with a trusted signature.

Edit: It appears that the unsigned checksum issue was already opened below and is a more general problem for all of the labs.fedora spins.

One thing to add is that on the download page, there are keys listed for IOT 2019, f30, f31, and f32, but not for f33 despite the top of https://labs.fedoraproject.org/scientific/download/index.html saying f33.