There are absolutely zero elements of Flash within AEM.Any Flash content was removed from the product back in AEM 6.3.

How deep is the path to the config?  The JCR Installer (org.apache.sling.installer.provider.jcr.impl.JcrInstaller) by default only looks to a max depth of 4. 

Can you share the output in the error.log from the HTML Library Manager? It likely spits out some more details on why the minification fails. Can you manually minify your JS directly on Google Closure? Here : https://closure-compiler.appspot.com/home

jsProcessor=[default:none,min:gcc;languageIn=ECMASCRIPT_2015;languageOut=ECMASCRIPT_2015]

With the Dispatcher log level at DEBUG can you share the log output for the vanityUrl request?  Do you have the vanityurls component installed?It's an old package from 2015 that oddly enough doesn't come with the product ootb. 

Of course. See : https://docs.adobe.com/content/help/en/experience-manager-65/assets/administer/metadata-schemas.html#apply-folder-specific-metadata  

Changing the logging level of the ROOT logger is tricky and often necessitates a server restart. This is also going to spit out GB of logging data.

The Wknd Tutorial is a good step by step guide. Start here : https://docs.adobe.com/content/help/en/experience-manager-learn/getting-started-wknd-tutorial-develop/overview.html 

See : https://sling.apache.org/documentation/the-sling-engine/servlets.html sling.servlet.methods is only applicable on registration of a servlet via sling.servlet.resourceTypes your servlet example is registered on sling.servlet.paths

The JDK Downloads are hosted on the Adobe Software Distribution pagehttps://experience.adobe.com/#/downloads/content/software-distribution/en/general.html  OpenJDK is still not supported. Generally you'd do the upgrade from 6.3 to 6.5 on JDK8.Then it's start AEM with Java11. If you're running into a...