How to set up web push notifications for a site with a large number of subdomains?

Question

Push technologies

I want to make push mailings for a site with a large number of subdomains. using a third-party service such as Onesignal or Push world. The difficulty is that when setting up, you must specify the site address and subdomains are considered separate sites there. We want to do the main point here without https, they will pop up the subscribe window, and the subscription itself will take place on the service domain. Yes, I know that this way the conversion will be worse, but it is necessary.