Customised QLViewController in Mac Catalyst shows then overwritten by system version

The standard Quick Look preview shows a Share icon and a link to an appropriate editor in the top right corner, when using Mac Catalyst. I subclassed the QLViewController to prevent this, the customised QLViewController initially shows then the standard version takes over. How do I prevent this?
Customised QLViewController in Mac Catalyst shows then overwritten by system version
 
 
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