Hi There, Just would like to share my experience with facing the same (x509: certificate signed by unknown authority) issue. After struggling with my Multipass Ubuntu for few days, I finally decided to check certificate, provided by https://canonical-bos01.cdn.snapcraftcontent.com/ and found out, that it was substituted by internet security software running on my host. Issue was simply resolved by disabling internet security software.
True canonical certificate should be issued by:
| Common Name (CN) | DigiCert TLS RSA SHA256 2020 CA1 |
|---|---|
| Organization (O) | DigiCert Inc |
| Organizational Unit (OU) |
Hope this may help somebody.