In order to get a useful DNS over TLS server configuration on macOS, I imported a network profile. After having installed this network configuration file, I did not see any new entry in the Network Settings graphical user interface. Only in the terminal, I can see it seems to be active:
[user attribute: profileIdentifier: com.quad9.tsecuredecs.HASH]
There are 1 user configuration profiles installed for 'user'.
In all tutorials on how to remove custom Network profiles, I see it appears in the GUI (for example Can't delete NextDNS profile from macOS Network Preferences). But in mine, there is nothing else than the default ones.