Recent updates to Android have made the filestystem weird and mad it hard to export the KML files. The remedy to this is using the files application, X-plore.
First go to the hamburger menue and go to database. Then click export as a KML. On recent Android phones a share menue will come up.
Second, click the X-Plore icon. This will open the application. Create a new folder and put the files in there. Lastly, wait a few seconds and go to your regular files application. Click the KML file and you can open it in Google Earth.
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