Big Sur Add trusted certificate via command line (Safari Can't establish a secure connection)
I think answered my own question and wanted to post it here in case anyone else runs into this.  In my case not only was it a self signed cert, but I was using a local host name which did not match the hostname on the certificate.
Therefore using the following command worked for all browsers tested:
 security add-trusted-cert -e hostnameMismatch-r trustRoot -k ~/Library/Keychains/login.keychain-db newcert.pem