this regards Opencard 3.0.xx-Maintenance and the current github pull from https://github.com/opencart/opencart-3
I am currently trying to setup a store, and I am using opencart 3 because my payment plugins are not available for opencart 4 yet. Installation goes through fine, but after logging in into the admin panel, and try to change the store logo or any product image, the image manager doesnt open. I get this instead:

I tried this with a current firefox esr build, chrome on linux, chrome on windows. When clicking onto the image to replace it, there is no network traffic(apache2 server log is not showing any activity, firefox http live headers doesnt record anything). There are no errors in developer console of firefox(F12)
Is there anything I can do to get the image manager working? Btw, this picture was taken with german language addon installed, however i get the same result on a naked fresh install.