Hello,
I am running into the same installation error on a J4 using the file J51_Chelsea_DemoInstaller.
I am following the instructions in the tutorial: https://www.joomla51.com/tutorials/demo-installer/setting-up-the-demo-installer
JLIB_INSTALLER_ABORT_REFRESH_MANIFEST_CACHE
Could not refresh manifest cache for extension: mod_sampledata
Has there been a critical change in the J4 install that might need attention, please?
Kind regards
Drew