EPUB CUSTOM COVER doesn't work

I’m trying to add a cover to my EPUB but can not get it to work?
Are there specific parameters? Nothing I’ve tried seems to work. Thanks for any help.
Using latest version, up to date.

EPUB EXPORT/ CUSTOM COVER IMAGE

Take the first Page in Writer for add and create a cover.

That works but doesn’t show up as the cover in the thumbnails when using iphone Books.

You may report it as a bug on Bugzilla.

Yep it’s there! Doesn’t seem like any movement on it since 9/2018? Bummer. tdf#119539