>> When it comes to handling recent spreadsheet formats in an independent manner, I can recommend this:
>>
https://xlsgen.arstdesign.com/Thanks, will take a look! I also found coolutils.com with "Total Excel Converter" that sounds as if it might do the trick.
"... They ne'er cared for us
yet: suffer us to famish, and their store-houses
crammed with grain; make edicts for usury, to
support usurers; repeal daily any wholesome act
established against the rich, and provide more
piercing statutes daily, to chain up and restrain
the poor. If the wars eat us not up, they will; and
there's all the love they bear us."
-- Shakespeare: Coriolanus, Act 1, scene 1