I hope you can get someone knowledgeable to help with this. I have the same problem. There must be another setting that greys out the option for turning off this notification.
The foolowing thread describes how to dismiss it until reboot, but it is still annoying if the phone is set to reboot every night:
Technically you have to tap it twice. Once to "maximize" the notification and then a single tap makes it go away until the next reboot. It would be nice to just get rid of it based on the available preference that I mentioned earlier where the setting is grayed out/disabled and can't be changed.
This seems to be the case unfortunately. At least it can be muted for the duration of the phone being powered until it's restarted. Hopefully Samsung will provide an update to allow for muting this notification completely.
For now those with the same issue can benefit from the "answer" provided by usera1T2V7ngSV so I'll mark that post as the answer. I appreciate those who posted on topic to try to help.
Totally agree. It's like having a notification display in your car constantly warning that 'you're not exceeding the speed limit', or warning you that 'the car is OK'.
Just turn off the notification from the settings. And it will go away forever I did that. no more notifications on my S9 plus. Lol just for that part beside i get all other notifications without any proble..