iMessage app/extension icon not visible on iOS 17

I'm trying to make a simple iMessage app, which I haven't done before so I'm not super familiar with the process.

I created a new project following the "iMessage App" template. I have an icon set named "iMessage App Icon" in the *MessagesExtension Assets catalog (and it says "Stickers Icon" in the top right corner). This is what was created by default with the project. I have filled out all of the icons in the iconset, and none of them have warnings.

When I install the app into an iOS 16 simulator and open iMessage, the icon appears exactly as expected. However, when I install the app into an iOS 17 simulator, or onto my iPhone 15 Pro running 17.3.1, and scroll through the new iMessage app interface, my app still has the default white grid-lines styled icon.

On basically every forum post I've read trying to solve this issue, I see people referring to "App Icon source in Target -> General", and in a normal app I would have that, however neither the host app target or the messages extension target have an "App Icons and Launch Screen" section. The only sections I have are "Supported Destinations", "Minimum Deployments", "Frameworks and Libraries", and "Development Assets". I'm not sure if this missing section is due to different versions of Xcode? (I am using 15.2) or if this indicates some larger problem with my project / the iMessage app template.

Any leads as to solve this would be greatly appreciated.