RSG2 (Version_4.5.2) for J3x is running under PHP 8.0. You may upgrade your site PHP version. Sadly RSG2 is not ready for J!4 now. We are still working at it.
Signs of life: RSG2 development is still active.
Not much has been done in the last few months due to another Joomla project..
The development is now picking up speed again
We are currently reprogramming the layout for root galleries on RSG2 for J!4
We try to get a similar look like the J!3 version but with improved properties for a smooth transition
New behavior with different folders is nearly finished in the backend. Now i concentrate on keeping the J3x structure so the transition to J4x will be as smooth as possible. Some functions will be missing though.
First image overview and slideshow seen. A "spike" in code development means a fast development hack to prove that a goal is reachable. RSG2 for J!4 proved now with spike code how to display a rudimentary image oview and a slideshow started by clicking on a image.