Made a fresh install on Windows with:
- Tomcat 9
- MySql 8
- xWiki 12.2
Loads perfectly when accessing the site localhost. I configured this in server.xml the access through a proper URL (I left the localhost config as it was, and added this config):
<Host name="xwiki.mycompany.net" appBase="webapps" unpackWARs="true" autoDeploy="true">
I can access the xWiki by using http://xwiki.mycompany.net and it loads without any browser errors in console (also no 404 in Network tab of developer tools).
I also moved the xwiki to the ROOT webapps of Tomcat.
When I access it this way some elements don’t load, such as the navigation. Here is a comparison screenshot between localhost and URL-access:
I tried with different browsers, from remote clients and also on the server itself, it makes no difference. Obviously localhost only works on the server itself 
Does anyone have any advice? I’m happy to share any configuration.
I do see one error during startup, but I think it’s unrelated:
2020-04-02 17:07:06,843 [main] ERROR .o.i.DefaultObservationManager - Failed to lookup listeners
org.xwiki.component.manager.ComponentLookupException: Failed to lookup component with type [interface org.xwiki.observation.EventListener] and hint [solr.availablelocales]
at org.xwiki.component.embed.EmbeddableComponentManager.getInstanceMap(EmbeddableComponentManager.java:245)
at org.xwiki.component.embed.EmbeddableComponentManager.getInstanceList(EmbeddableComponentManager.java:225)
at org.xwiki.observation.internal.DefaultObservationManager.initializeListeners(DefaultObservationManager.java:166)
at org.xwiki.observation.internal.DefaultObservationManager.getListenersByEvent(DefaultObservationManager.java:132)
at org.xwiki.observation.internal.DefaultObservationManager.notify(DefaultObservationManager.java:283)
at org.xwiki.component.internal.StackingComponentEventManager.sendEvent(StackingComponentEventManager.java:151)
at org.xwiki.component.internal.StackingComponentEventManager.flushEvents(StackingComponentEventManager.java:92)
at org.xwiki.container.servlet.XWikiServletContextListener.contextInitialized(XWikiServletContextListener.java:124)
at org.apache.catalina.core.StandardContext.listenerStart(StandardContext.java:4690)