For many releases, Rancher rejects self-signed certs, which makes it impossible to use from the command line. Here is finally a workaround!

If you're getting something like:

# rancher --version
rancher version v2.9.0
# rancher login https://rancher..sslip.io --token token- --skip-verify      
FATA[0000] Get "https://": tls: failed to verify certificate: x509

The workaround is:

Download cacert from the Rancher UI, go to Global Settings --> Show cacert --> Copy cert value and paste to local file

rancher login https://rancher..sslip.io --token token- --skip-verify  --cacert