Why is it when I’m trying to install ZFS on Debian Trixie, I get a message that the release can’t be found?

I’m trying to install ZFS on a fresh install of Debian Trixie using these instructions.

Running sudo apt install -t stable-backports zfsutils-linux results in:

E: The value ‘stable-backports’ is invalid for APT::Default-Release as such a release is not available in the sources”

Just like the instructions say might happen. I followed the instructions and now when I run tail -n 1 /etc/apt/sources.list I see:

deb http://deb.debian.org/debian trixie-backports main contrib non-free

But I’m still getting the same error:

E: The value ‘stable-backports’ is invalid for APT::Default-Release as such a release is not available in the sources”

Tried changing stable-backports to trixie-backports and the same error persists.

Running sudo apt install zfsutils-linux results in:

Package zfsutils-linux is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source

Error: Package ‘zfsutils-linux’ has no installation candidate

The package seem to exist though: https://packages.debian.org/trixie/zfsutils-linux