Hello, when the "Updates" icon in the systemtray is pressed , the program "Discover" obviously starts downloading the list of the updates from Debian repositories, but if the program window is closed, then the systemtray notification area is filled so much with pop-up messages belonging to Discover, that my laptop begins to slow down. Just to get an idea of what's happening, give a look at my screenshot.
I don't know if this can be considered a bug, but what I would like is to disable this kind of notifications that are meaningless to me and get along with Discover.
https://imgur.com/gallery/ac6iI3w

In System Settings -> Personalisation -> Notifications -> Applications: Configure.. disable the notifications for Discover

Thank you Mamarok, I tried your suggestion so I disabled Discover notifications entirely but the pop-up messages keep going. I think it is something underlying to Discover that is generating the messages, the author is "kded5".

Try disabling the low priority pop-ups

That's it! Thank you!