Addressing comments from @paulmedynski

Author: benrr101

src/Microsoft.Data.SqlClient/netcore/src/Microsoft.Data.SqlClient.csproj

@@ -41,8 +41,8 @@
 
   <!-- OS Constants ==================================================== -->
   <PropertyGroup>
-    <DefineConstants Condition="'$(OSGroup.ToUpper())'=='UNIX'">_UNIX</DefineConstants>
-    <DefineConstants Condition="'$(OSGroup.ToUpper())'=='WINDOWS_NT'">_WINDOWS</DefineConstants>
+    <DefineConstants Condition="'$(OSGroup.ToUpper())'=='UNIX'">$(DefineConstants),_UNIX</DefineConstants>
+    <DefineConstants Condition="'$(OSGroup.ToUpper())'=='WINDOWS_NT'">$(DefineConstants),_WINDOWS</DefineConstants>
   </PropertyGroup>
 
   <!-- Compiled Files ================================================== -->

src/Microsoft.Data.SqlClient/netfx/src/Microsoft.Data.SqlClient.csproj

@@ -103,7 +103,7 @@
 
   <!-- OS Constants ==================================================== -->
   <PropertyGroup>
-    <DefineConstants Condition="'$(OSGroup.ToUpper())'=='WINDOWS_NT'">_WINDOWS</DefineConstants>
+    <DefineConstants Condition="'$(OSGroup.ToUpper())'=='WINDOWS_NT'">$(DefineConstants),_WINDOWS</DefineConstants>
   </PropertyGroup>
 
   <!-- Compiled Files ================================================== -->

src/Microsoft.Data.SqlClient/src/Microsoft.Data.SqlClient.csproj

@@ -17,8 +17,8 @@
 
     <!-- NOTE: These constants are prefixed with _ to keep them separate from .NET 5+ precompiler -->
     <!--     flags. Those only apply to OS-specific target frameworks, and would interfere here. -->
-    <DefineConstants Condition="'$(TargetOs.ToUpper())' == 'UNIX'">_UNIX</DefineConstants>
-    <DefineConstants Condition="'$(TargetOs.ToUpper())' == 'WINDOWS_NT'">_WINDOWS</DefineConstants>
+    <DefineConstants Condition="'$(TargetOs.ToUpper())' == 'UNIX'">$(DefineConstants),_UNIX</DefineConstants>
+    <DefineConstants Condition="'$(TargetOs.ToUpper())' == 'WINDOWS_NT'">$(DefineConstants),_WINDOWS</DefineConstants>
   </PropertyGroup>
 
   <!-- Embedded resources ============================================== -->

src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/LocalAppContextSwitches.cs

@@ -465,9 +465,9 @@ public static bool UseManagedNetworking
         }
         #else
         /// <summary>
-        /// .NET Core on Unix does not support the native SNI, so this will always be false.
+        /// .NET Core on Unix does not support the native SNI, so this will always be true.
         /// </summary>
-        public static bool UseManagedNetworking => false;
+        public static bool UseManagedNetworking => true;
         #endif
 
         #else