npub15c0uz3l55klsrq6l9zlvmtkvxwv2wy7q0rm7y249qkmzxpaj5gks5thxke (npub15c0…hxke) this is a sample of the notifications
I think it could be related to which is showing the notification is the Vivaldi Helper.
I tried the same notification using Orion Browser (which uses WebKit), and notifications are well displayed.