When using internal GPS of the phone/tablet on Android, ellipsoid altitudes are reported (there's a ticket #2615 to convert those to geoid altitudes so that it's consistent with external GNSS).

BUT with Android 15+ there's a bug in Qt and the mobile app reports geoid altitudes instead 🤯 (the older Android versions should still return ellipsoid altitudes). There is a bug fix in Qt (qt/qtpositioning@80a0ad5) but not available in a released version of Qt as of today.

Workaround: switch to "Internal (fused)" GPS receiver - that will consistently report ellipsoid altitudes.

More details:

• Qt 6.8+ can optionally provide geoid altitudes on Android 14+ (using "useMslAltitude" parameter - off by default) - https://doc.qt.io/qt-6/position-plugin-android.html - see qt/qtpositioning@0f3efd9
• In Android 15+ the geoid altitude seems to be always present in location, and Qt incorrectly thinks that the "useMslAltitude" has been turned on - see https://bugreports.qt.io/browse/QTBUG-106049