some info here: Generic Cloud (Cloud-init) | AlmaLinux Wiki
bit confusing as there’s versioned keys and not one for the full dvd1 iso only cloud/live.
basically:
curl -s https://repo.almalinux.org/almalinux/RPM-GPG-KEY-AlmaLinux-9 -O
curl -s https://repo.almalinux.org/almalinux/9.0/live/x86_64/CHECKSUM -O
curl -s https://repo.almalinux.org/almalinux/9.0/live/x86_64/CHECKSUM.asc -O
gpg --with-subkey-fingerprints RPM-GPG-KEY-AlmaLinux
gpg --import RPM-GPG-KEY-AlmaLinux
gpg --verify CHECKSUM.asc CHECKSUM
sha256sum -c CHECKSUM