LRC 15.2.1 arm64. I do not have an apply button in the removal section.

There is no Apply button, found dust spots are removed automatically when you check Apply.

This is what I see after checking Apply, the ring represents a removed spot, seen when hovering the mouse over the image.

Hi ​@Heartwood, Welcome to the Lightroom Community forum! To better help you with this issue, we would like a few more details. Can you send your system info and a few screenshots of what you’re seeing? You can find your system info by going to Help > System Info, copying and pasting it into a text file, and attaching it here.

In the meantime, try resetting your Lightroom Classic Preferences. Please refer to this Helpx article for steps.  https://adobe.ly/3HsQXpA It is recommended to back up your catalog before resetting preferences. You may refer to this article for more information:  https://adobe.ly/4dW8vqF.

I hope this helps! ^CH