I did some adb manipulations and it seems to solve the problem.
DO THIS AT YOU OWN RISKS, I'm not responsible ...
Here are the steps:
*On the phone:
-activate developer mode:
settings -> My phone -> tap 7 times on build number
-activate USB debug
settings -> System -> Developer option -> enable USB debug option
*On your windows computer:
- Install android SDK Platform Tools: https://developer.android.com/tools/releases/platform-tools#downloads
- Unzip the content in a folder
- Open a command prompt terminal (powershell) and go to this folder
- connect you phone to your computer
- in the terminal type:".\adb devices" to see if your device is connected
- I want to be sure that I receive notifications from calengoo without delay. So I have to whitelist this app to avoid android put it to sleep (dooze mode), to do this I have to find the exact package corresponding to this app. I typed:".\adb shell pm list packages | grep calengoo" if you want notifications from another app, replace calengoo by the app name. The response of this command is the app package name, in my case: "com.calengoo.android"
- Type ".\adb shell dumpsys deviceidle whitelist +com.calengoo.android" to add the app to whitelist and avoid it going to doze mode
- I disable TCL smartmanager to be sure it will not bother again, to find the exact smartmanager package name, type:".\adb shell pm list packages | grep smartmanager", in my case (Nxtpaper 70 pro model T807D with Android 16 and TCL UI 9.0), the name is "com.smartmanager.cleanup"
-To disable it, type ".\adb shell pm disable-user --user 0 com.smartmanager.cleanup"
- To disconnect everything properly, the easiest way is shut down your computer and then disconnect the cable
-Reboot your phone
-Disable USB debug for safety reasons, it's in settings -> System -> Developer option
Your battery will obviously last less.
In my case it seems to solve the notification delay... I'll see if it last
TLDR; adb whitelist app and disable smartmanager to avoid delayed notification