In Lucee 126.96.36.199 and prior versions, cfhtmlhead works when used in OnRequestEnd where the output attribute is set to false.
In Lucee 188.8.131.52 the same code fails to output anything in the HTML head element;
There are two ways to work around the issue in Lucee 184.108.40.206;
1. Leave output="false" in OnRequestEnd, but set Buffer Tag Body Output to "true" in the Lucee admin
2. Use output="true" in OnRequestEnd, and leave Buffer Tag Body Output set to "false" (which is the new default in 5.3)
This seems like a regression in Lucee 5.3.x related to the new default value for Buffer Tag Body Output.
Test case to reproduce the issue;