The beta rom is missing some notification settings like grouped notifications, balloon notifications, priority and non-priority notifications! all these settings in China beta as well as globally!
Exact, even on his Redmi 9 my friend have this problem

Just be sure to go on app settings > choose apps > notifications > choose sound (often empty/no sound)
I have this "problem" on a lot social/sync apps like Signal, Email, WhatsApp & cie...
21.11.17 is out, changelog :
File Manager
- Added the ability to hide pictures on recent pages
- Add category entry editing function on the mobile page
- Optimize the style of the recent page and each file classification page
- Optimize the filter panel style
- Optimize the grouping of recent pages
System
- Fixed the disappearance of Gaussian blur in the volume panel (Redmi K40, Xiaomi 10S)
Status bar, notification bar
- Fix the problem that the top of the floating notification is displayed abnormally when the floating notifications of different heights arrive at the same time (Redmi K40, Xiaomi 10S)
- Fix the problem that the time sequence of notifications sent by apps is not updated in the notification management (Redmi K40, Xiaomi 10S)
- Fix the issue that notifications will appear when sliding the screen when the lock screen pictorial displays the wallpaper (Redmi K40, Xiaomi 10S)
- Fix the problem of image retention when clicking the blank area to close the notification bar (Redmi K40, Xiaomi 10S)
EDIT : Feedback, new Fastboot UI from 21.11.17, no little robot anymore ! lol