landscape-client leaking the private URL of the server

landscape-client 19.12-0ubuntu4.2

my client.conf contains

    [client]
    url = https://my.super.secret.company.com/message-system

that allows to reach a private landscape-server whenever I am on the company's network.

When I am not connected on my company's network, I expect no traffic to be attempted to the private landscape-server. In practice though, the client will keep trying to connect and send DNS queries to resolve my.super.secret.company.com (they all fail).
This is unencrypted traffic to a public DNS server, so my laptop is leaking the private URL of the landscape server. I would like to prevent this traffic, basically:

"my.super.secret.company.com" name should never be sent to a DNS server not owned by my company.

(of course I would love a generic solution as landscape-client is not the only one doing this :) but it is the worst offender on my laptop)