I set the url of Plesk with let’s Encrypt and using mydomain:8443 everything is ok, but if I use the ip address:8443 the connection is not trusty.
There’s a way to avoid the possibility to make the login using the server ip address?
Plesk IP address cannot be secured with a Let's Encrypt certificate, as Let's Encrypt does not support securing IP addresses.
In order to secure a Plesk IP address, it is required to purchase a certificate from Certificate Authorities that provide such an option. An example of such certificate is OrganizationSSL certificate by GlobalSign, which allows securing public IP addresses.