Steps to reproduce the issue

use a joomla v4.03, that is installed on a sever (not local!), i used php 8
goto the backend and install the attached minimum demo module

Expected result

it gets installed

Actual result

getting the error: Undefined constant "JPATH_"

System information (as much as possible)

i used a fresh j4.0.3

Additional comments

i didn't see it with a local installation. For better analysis i will also add an attachment of the debug info
mod_demo-min.zip

Maybe, there is a wrong coding in my module, it is my first attempt to do so in Joomla 4 ;-)