The development of the current Slideshow app is currently suspended. We have plans for the realization of a new rewritten version optimized for the new systems but for the moment we are not able to provide a date or say anything official about it.
Regarding the current version we can say the following:
1. If the system warns you that the application is not optimized but opens it, you can continue to use it (but you will not benefit from the new features of the system designed for optimized apps).
2. If the application stops working following a system software update, we recommend switching to a different application than ours.
Here you can find two blog articles from other software houses that review Slideshow alternatives:
Keep in mind that some of the products mentioned are created by the author of the article itself, so always evaluate the product before buying it.