I previously developed a workflow in which I would digitize line segments in a shapefile that would ultimately be converted to a CSV, and the geometry stored in a WKT field. When this workflow was created I needed the WKT field to be in Linestring as opposed to Multiline String, and I was able to accomplish this by utilizing the Multipart to Singlepart tool in Arcmap. After executing this tool I could bring the shapefile into QGIS and export the shapefile as a CSV with a Linestring WKT field.
It seems something has changed outside of this workflow that no longer allows the establishment of Linestring within a WKT field. I have attached a sample CSV that I have not been able to convert to linestring. If anyone has any solutions outside of programmatically solving this it would be greatly appreciated!!