Is it safe to manually download a package from this site and then install the .deb file using apt? Is there anything more secure about using apt to download the package?
Is it safe to manually download a package from this site and then install the .deb file using apt? Is there anything more secure about using apt to download the package?
No, it’s considerably more safe than that. Unless the .deb has been cryptographically signed by the Debian maintainers, it won’t install, no matter where you download it from.
For this reason, apt intentionally did not support any secure protocols (such as https) until just a few years ago. There’s no point to downloading it securely or from a trusted source: all the security is in the signature verification. (And insecure protocols like http are usually easier to cache/proxy)
I find that hardly unlikely, you can get several .deb files that are most definitely not signed by Debian maintainers, e.g. zoom, all of the packages from . Signatures of packages can be done by anyone, and apt can be configured to accept multiple keys so each distro can choose which ones to accept.
Also, AFAIK, apt only checks signature for packages it itself downloads, which is why you need to add new keys for adding repos but not when installing .deb files. That being said, when I install .deb packages on debian based distros I use dpkg so it might be that apt does check, but you can definitely install deb packages without it.