I thought it was built in the rom working. but when i tried to open it didnt . So i tried this magisk module which works on my S20 plus .
Even after removal of the module its still present in settings and opens so i thought it was a working function so i asked.
Now im thinking this module has installed the apk in system and thats why even after removing module its there
I guess i should remove this applock apk then if it was not present in the rom. im not sure as i never checked earlier applock