Child theme custom template not being picked up

I’m trying to use a custom page template. Following the instructions on https://www.wpdownloadmanager.com/doc/template-files/ I’ve copied the supplied page-template-default.php, made some ajustments and saved the file into /{child-theme}/download-manager/page-templates/ and selected “Default Template” in the Package settings. Unfortunately it still picks up the “Default Template” in the plugin folder. I’ve also tried placing page-template-default.php into /{child-theme}/download-manager/ and I’ve tried changing the filename and WPDM Template name. The only way I’ve managed to use my custom template is to save it into /wp-content/plugins/download-manager/src/Package/views/page-templates/{custom-name}.php. Unfortunately this gets deleted when the plugin is updated. How do I use a custom template in a child theme?