Seems fairly simple:
Shared Async Function LoadMap() As Task(Of DataTable)
Const url As String = "https://gitlab.com/wireshark/wireshark/raw/master/manuf"
Dim result As New DataTable()
result.Columns.Add("MacAddress", GetType(String))
result.Columns.Add("Manufacturer", GetType(String))
Dim http As New HttpClient()
Using response As HttpResponseMessage = Await http.GetAsync(url)
response.EnsureSuccessStatusCode()
Using stream As Stream = Await response.Content.ReadAsStreamAsync()
Using reader As New StreamReader(stream)
Dim line As String = reader.ReadLine()
While line IsNot Nothing
If line.Length <> 0 AndAlso line(0) <> "#"c Then
Dim parts As String() = line.Split(Microsoft.VisualBasic.Constants.vbTab)
result.Rows.Add(parts(0), parts(1))
End If
line = reader.ReadLine()
End While
End Using
End Using
End Using
Return result
End Function