The notification shown on Wi-fi tethering is still using icon on the right side. This is harder to replace than other notifications, because
- The icon seems to reflect current signal strength
  (need investigation what are actually shown, and careful verification after replacement)
- The notification is hard to reproduce physically (for me)

Notification title & message are:
- Title: Wi-Fi available via phone
- Message: Data connection available from your <Google Pixel XL>

https://cs.chromium.org/chromium/src/chrome/browser/chromeos/net/tether_notification_presenter.cc?l=80&rcl=8847e91cd91862d25596bb47532bd6a3af4540ed

elizabethchiu@'s team owns this notification.