When using MoPub's Adplacer feature, a native ad renderer needs to be set up. This set up needs to contain an additional reference to our Mediation event so that Smaato native ad responses can be placed in collections:

  MPStaticNativeAdRendererSettings *nativeAdSettings = [[MPStaticNativeAdRendererSettings alloc] init];
    nativeAdSettings.renderingViewClass = [MoPubNativeAdCell class];
    nativeAdSettings.viewSizeHandler = ^(CGFloat maximumWidth) {
        return CGSizeMake(maximumWidth, 312.0f);
    MPNativeAdRendererConfiguration *config = [MPStaticNativeAdRenderer rendererConfigurationWithRendererSettings:nativeAdSettings];

    // ==== REQUIRED: Add support for Smaato custom event ====
    config.supportedCustomEvents = @[@"SOMAMoPubNativeCustomEvent"];
    // ==== REQUIRED: Add support for Smaato custom event ====
    self.adPlacer = [MPTableViewAdPlacer placerWithTableView:self.tableView viewController:self rendererConfigurations:@[config]];

This setup allows placing and loading the ads into both UITableView and UICollectionView.