I have noticed similar notifications recently when playing YouTube videos, whether on YouTube, or embedded in other websites.
I’m using LineageOS 15.1 (based on Android 8.1) without Google apps/services, and I’ve installed Brave from Yalp Store (so it’s the same APK as the one from the Play Store).
Another user has reported the same problem: Android - LineageOS 16 - Get Google Play Services Notifications