In Canada, see GPS-H from Canadian Geodetic Survey. As the name implies it's suitable for point records and not lines & polygons, and unlikely a good fit for mass points. Input formats are ascii text files like CSV.
GPS-H allows conversion of GNSS ellipsoidal heights h, that are either in
NAD83(CSRS) or ITRF, to orthometric heights H (heights above ...
If you are working with old wgs84 coordinates you can substitute etrs89 with wgs84.
Etrs89 is wgs84 attached to the european continental plate. Wgs84 observations in 1989.0 are identical to Etrs89. Starting from 1989 there is a shift of approx 2.5 cm per year.
So if your details are less than a meter, the difference between etrs89 and wgs84 is academic.