Hi Ryan
Just want to provide some feedback, I installed JCE 2923.zip on a new joomla 4.2 beta and received the message below during the installs. The editor install and seems to be working fine. I then tried the latest beta version (2925b2) The error is not presented during install but when I try to access the JCE control panel it tells me I don't have permissions though, I am logged in as the super user.
2923 msg
Call to undefined method Joomla\CMS\Filesystem\File::read()
2925b2Beta msg.
403 You don't have permission to access this. Please contact a website administrator if this is incorrect.