GetConnectionsRequest has property Strategy which is of type string, so I made a conclusion that I can query several connections with a different Strategy (aka connection types) at once. But it failed with an exception in your client before sending a request.
Here you can see an Exception Stack trace.:
System.ArgumentException: An item with the same key has already been added. Key: strategy
at System.Collections.Generic.Dictionary`2.TryInsert(TKey key, TValue value, InsertionBehavior behavior)
at Auth0.ManagementApi.Clients.ConnectionsClient.GetAllAsync(GetConnectionsRequest request, PaginationInfo pagination)