I feel like your threat model is not realistic. It is way more likely that you will be running malicious and/or vulnerable code that was packaged appropriately by the actual package maintainer than for a CA compromise to allow an attacker to inject a malicious package during a MITM attack while retrieving an OCI image from a container repository. Like, yes, you shouldn’t 100% trust your ISP or your DNS server, but if you’re that paranoid, you shouldn’t trust your distro’s repository either. You should be building everything from source.