This version of Unity is unsupported.
Removed in version 2019.2.22

MasterServer.PollHostList

Obsolete public static HostData[] PollHostList();

Description

Check for the latest host list received by using MasterServer.RequestHostList.

You can clear the current host list with MasterServer.ClearHostList. That way you can be sure that the list returned by is up to date.