Hello
Thank you for your question and reaching out.
I can understand you wish know more about how DC locator works for 2016 and 2019 server.
By default, DC Locator does not consider any site that contains a read-only domain controller (RODC) when it determines the next closest site. In addition, when the client gets a response from a domain controller that runs a version earlier than Windows Server 2008, the DC Locator behavior is the same as when then setting is not enabled.
For example, assume that a site topology has four sites with the site link values in the following illustration. In this example, all the domain controllers are writable domain controllers that run Windows Server 2008 or newer.
Below is reference article from Microsoft which is applicable for Windows 2016 , 2019 and 2022 server.
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