Common map leaflet data layers and features not working

v3 does not really support layers. v4 does, but it's still a few weeks from beta1.

Could you describe exactly how I could recreate your scenario do get an idea what to achieve?

Sure - in the demo view
select settings for commonmap
set map provider leaflet
go to data layers & features
check marker cluster
check marker popup
click apply
check the preview
none of the markers cluster,
I can click a marker, but just get a blue box
mousing over shows some data.

What I want is the markers to cluster
Be able to click an icon, get a title, and click the title to navigate to content as if I had selected the Leaflet format option.
Does that help?