Solved
Unable to validate node types since project ... is not associated with a server or the server is not started.
I am getting this error which is described in one of the AEM tutorials
Getting Started with AEM Sites Part 2 - Creating a Base Page and Template

Unfortunately, the suggested fix does not work:
- First issue is, Eclipse does not allow removing Dynamic Web Module through the UI.
- Second issue is, if you forcibly remove it by editing /ui.apps/.settings/org.eclipse.wst.common.project.facet.core.xml, the actual problem is still not solved.
Any other ideas?