I'm also using Galaxy M21, but you cannot see the daily data usage in notification bar, you can see the monthly data usage in settings.
1.Go to settings and click connections. 2.In connections, data usage option and click them. 3.Now you can see the monthly data usage and click the Billing cycle and Data warning. 3.Click the option and set the data warning in 'ON' 4.In notification bar you can see monthly usage. 5.For daily data usage in the start billing cycle on you have to set the DAY cycle for daily..
(Or) You have to use the Ultra Data saving,with Samsung Max
