Hi Alexander,
I moved to new version 26.5 and here my results:
Please see:
Test data(input/output/QGIS)
5375-Gml Kml.7z (45.7 KB)
Thanks,...Bug 5375: Gml to Kml- Conversion succeeded, output in QGIS -...(gml3.gml) is incorrect for conversion. No root element declaration...