Hi Alexander,
I moved to new version 26.5 and here my results:
Please see:
Input-Gml - seen in QGIS.
Gml->GeoJson- not seen in QGIS.
Gdb->GeoJson- not seen in QGIS.
Test data(input/output/QGIS)
5454 Gml-Gdb.zip …...Bug 5454: Gml to Gdb- Conversion succeeded, output in QGIS- Empty...