How to update to JEM 4 for Joomla 4 and PHP 8

• Update to JEM 2.3.6
• Make a backup!
• Disable the JEM extensions, all jem plugins, all JEM modules
• (During upgrade process, it suggested to switch to Joomla3 default template "Protostar")
• To prepare the update from Joomla3 to Joomla4, go to Components > Joomla! Updates, choose Options and in Update Channel choose Joomla Next.
• Save.
• Then you get the informations about which other components are not ready. Perhaps I have to disable/uninstall other components/modules/plugins not prepared for Joomla4)
• Update to php 8+
• Then upgrade from Joomla3 to Joomla4.
• Install JEM 4
• Before switching to the frontend, change the positions of the JEM-modules and the main menue, to the positions of your new Joomla4 template (e.g. the Joomla4 default template "cassiopeia"!
• Enable all JEM 4 (component, modules, plugins)
• Adapt the JEM settings (there are changes: e.g. datetime format)
• Check everythink if it works!
• Finish :-)