If you want to use eglfs, you need run like this :
systemctl stop weston
export QT_QPA_EGLFS_KMS_CONFIG=`pwd`/eglfs.json
export QT_QPA_PLATFORM=eglfs
export QT_QPA_EGLFS_INTEGRATION=eglfs_viv
The eglfs.json
{
"device": "/dev/dri/card1",
"outputs":[
{"name": "HDMI-A-1","mode":"1920x1080"}
]
}