I support this from the UX side. Let me know if I can help at all.

Let's make this public :).

 Issue 729113  has been merged into this issue.

I should note that we do get the fancy bubble already for WebApks, but the site can't customize it :(

Is that Android's default behaviour for notifications posted without a channel? (+awdf)

We explicitly disable all sorts of bubbles for Chrome's notification channels.

I think so. Honestly as a user, I liked it :)
Keep in mind this is different than a generic chrome notification and without a site, it's unclear that the bubble is helpful. But for example for facebook webapk, that bubble is telling me something

Yeah, I'm a fan too :). Maybe we should offer an opt-out instead of an opt-in if we think it's applicable to a majority of WebAPKs?

Sure, I think we could offer an opt-out / potential customization opportunities (I haven't looked at what android provides)

Android allows apps to specify for a given notification whether they wish the launcher to use the notification's big, small or no icon for the badge, via Notification.Builder.setBadgeIconType - this may or may not be respected by the launcher:

https://developer.android.com/reference/android/app/Notification.Builder.html#setBadgeIconType(int)

We currently call setShowBadge(false) on all notification channels before creating them, including the Sites channel for (non-web-apk) web notifications. I'm not sure what the default would be if we didn't explicitly call that, I think it changed at one point, and might depend on the launcher, so we call it explicitly to be sure that we don't ever show a dot on the chrome logo.

Small update to #10 - Android O now just shows a dot as the default badge, or a number if the app calls Notification.Builder.setNumber(). The icon type provided to setBadgeIconType is only displayed in the app-icon longpress menu (at least on the default Pixel launcher).