Thanks! I just tried this now, with no luck 
This link suggests a major purge of everything Java from the system and then a fresh re-install, so I am trying this now to see if it helps…
But it seems the openHABian Zulu-11 installer isn’t properly generating a “cacerts” file at all, so this still may not work. I may try installing Java the old way/directly, without openHABian. Or just go back to Java 8…