Hey,
just tried to upload images into a simpleviewer (showcase) gallery. unfortunatlyi get a yellow warning triangle with the following text "Creation of dynamic property ThemSet:::$config is deprecated in themeset.php, line 60
Even tried clean install.

Showkase pro: 1.76 
PHP: 8.0 (also tested 8.1 and 8.2)

Example Picture attached

Any ideas? Thanks
Sponch