Thats why we use cryptography.

You could host the release on the police servers and they still couldn’t get a client with a pinned public key to download a malicious version, because releases are signed.

That said, while TAILS takes security seriously, you shouldn’t just expect all package managers to update themselves securely. This is why you want to avoid these new tools that don’t care about security, like flatpak, snap, brew, chocolaty, docker, pip, npm, etc