Not sure how things are right now, but I think on iOS you can't zap posts on any client, it’s against apple policy about payments in apps. It might be possible to go around it using PWA. More about PWA: https://juraj.bednar.io/en/blog-en/2023/08/01/goodbye-app-lets-move-from-the-centralized-stores/
PWAs solve the issue of wallets being deplatformed, not the issue of zap features being removed from the apps. Nonetheless, Damus seems to have solved the issue with the usage of that external script. I was ignoring the fact that Primal lacks zap features on posts for IOS users.