unwat Thanks, I was reading some of those links just now.
My question is, does Vanadium use Firebase Cloud Messaging as the push service? If so, it follows that Google Play Services are required for push notifications from Vanadium. From searching online, Chrome uses Firebase Cloud Messaging as the push service.
To be clear what I mean about the push service, from: https://web.dev/push-notifications-overview/#send
The push service receives [the web developer's] request, authenticates it, and routes the push message to the appropriate client...each browser uses whatever push service it wants.
I guess to answer that question, I need to go and install some PWAs using Vanadium in a user profile without Google Mobile Services, and see if push notifications work.