XWiki not working after apt upgrade from 15.3 to 16.3 on Ubuntu 20.04.6 Workstation

Not a tomcat expert, /var/log/tomcat9 has many files:

root@obl-ubuntu:/var/log/tomcat9# ls -ltr | tail -5
-rw-r----- 1 tomcat adm     7486 May  7 17:11 localhost_access_log.2024-05-07.txt.gz
-rw-r----- 1 tomcat adm     9418 May  8 10:00 localhost.2024-05-08.log
-rw-r----- 1 syslog adm 14272752 May  8 10:00 catalina.out
-rw-r----- 1 tomcat adm    14548 May  8 10:00 catalina.2024-05-08.log
-rw-r----- 1 tomcat adm      259 May  8 10:02 localhost_access_log.2024-05-08.txt

BUT this log file suggests there is a JRE version problem:

root@obl-ubuntu:/var/log/tomcat9# head -4 localhost.2024-05-08.log 
08-May-2024 10:00:23.295 SEVERE [main] org.apache.catalina.core.StandardContext.listenerStart Error configuring application listener of class [org.xwiki.container.servlet.XWikiServletContextListener]
	java.lang.UnsupportedClassVersionError: org/xwiki/container/servlet/XWikiServletContextListener has been compiled by a more recent version of the Java Runtime (class file version 61.0), this version of the Java Runtime only recognizes class file versions up to 55.0 (unable to load class [org.xwiki.container.servlet.XWikiServletContextListener])
		at org.apache.catalina.loader.WebappClassLoaderBase.findClassInternal(WebappClassLoaderBase.java:2424)
		at org.apache.catalina.loader.WebappClassLoaderBase.findClass(WebappClassLoaderBase.java:865