I’ve tried this on the newest version of Local 5.2.8+2771, and I’ve tested brand new installs on both PHP 7.3.5 and PHP 7.4.1 (current versions at the time of this post). It would seem that 7.4.1 does not create image thumbnails from jpg/jpeg images when uploaded to the media library. However, a barebones install (clicking the fat green + and that’s it) with 7.3.5 does everything as expected.
When running the Regenerate Thumbnails plug-in it gives this error:
The current image editor cannot process this file type.
I’ve tried it, with multiple file types of the same image and multiple barebones install, and it seems that this is isolated to only jpg/jpeg images, leading me to think there’s an extension issue with the current compiled version of PHP 7.4.1.