There is no app lock protection

[rameshkram]

This is sad news because of not having the app lock in galaxy m21 till now 

[tarun001]

Try to download s secure app from galaxy store

[rameshkram]

Thanks

[Tejavinni]

Remember S secure **bleep**... anyone can easily uninstall that and then your data will be exposed..m

[rameshkram]

That is not a good thing

[rameshkram]

If that app is Uninstalled app locks will not works

[Chanakya_Reddy]

Bro see my post.
https://r2.community.samsung.com/t5/Tech-Talk/Solved-Inbuilt-AppLock-Issue/td-p/9606969
This will definitely work in your M21.
No need of 3rd party apps and no need of s secure.