If I try to check e.relatedTarget for dragleave event, in Safari (v14.1.2) it is always null.
You can see it here (add console.log) — https://jsfiddle.net/zfnj5rv4
In Chrome it works fine.

This page says that Safari supports MouseEvent.relatedTarget.
This page says that DragEvent inherits properties from MouseEvent and Event.

Is it broken or never worked?