You can use sling mapping to remove content/dam. Check [1] for more details.[1] Resource Mapping

Looking forward to the session and hearing from the Experts!

I just tried this on my side and OOTB text component works without any issues on AEM 6.4Can you try to remove the custom code and test if you still see the same issue?Another way to test is to point the "sling:resourceSuperType" to "core/wcm/components/text/v2/text"

Can you go to <host>:<port>/useradmin and check if "preupgrade-service" is an actual service user in AEM?

As far as I can check, no changes are required on apache.  Check details below for the detailed description of three types of "Include Type":Apache SSI – Apache Server Side IncludesApache HTTP Server is set up as a caching proxy in front of the AEM. This means that the include will be done by the ht...

For color, you can add color picker plugin as described at - Experiencing Adobe Experience Manager - Day CQ: AEM 62 - Touch UI Dialog RTE (Rich Text Editor) Color Picker Plugin

Check the error.log file and grep for the bundle name to check for various livecycles of the bundle. Lastly, you can alsdo setup a DEBUG logger on the bundle package which is not getting started.

Theo,Thanks for sharing the knowledge and contributing to the AEM community.

Can you try to remove the overlay under apps by creating a package? Also, try to check if you see the same issue for asset folders with 1/2 assets.

Usually, this error is observed when the service user mapping is missing to the pre-upgrade bundle. Can you add the mapping as per below and check if you still get the same issue?Go to the Web Console at http://serverhost:serveraddress/system/console/configMgrSearch for Apache Sling Service User Map...