Sometime when you try to export a new layer to the GeoPackage format in QGIS you'll get a very annoying and possibly alarminglooking error message with loads of lines saying the same thing. Usually it will start something like this:

Export to vector file failed.
Error: Feature write errors:
Feature creation error (OGR error: failed to execute insert : UNIQUE constraint failed: etc etc....)

The solution is quite easy but it may not be easy to find that out online. All you need to do is untick one field option when exporting to a new layer, as I show in this short video.

I hope this saves you some time and pain.

See my intro and intermediate QGIS courses for more: https://www.udemy.com/user/alasdairr...