Remove a package (upday) from stock theme

I'm new to android so please forgive my maybe trivial questions. So far I've been able to root my J3-2017 (TWRP+SuperSU+Nougat) and now I can access the internal file system using adb shell. My purpose is to debloat my device. I've been able to manually delete Microsft apps (*) but I don't seem to find a way to remove UpDay which, apparently, is packaged inside the default theme. The question is: does anybody know a way to remove such apps from a theme? Thank you (*) this is how I did remove Office: adb shell su mount -o rw,remount /system find / -iname '*Excel*' . . . rm /data/data/com.microsoft.office.Excel ...