Your issue is that the node uses the interop shipping with excel to interpret the excel file… Without the interop no decoding
But you could probably write your own node for openoffice if they have an open API
There are related topics here: (Suggesting to try an ODBC connection).
And here covering how Dynamo actually needs to open up an excel file in excel to alter and read the information contained in the file… (Which is also a reason to use .csv or .xml files instead).