Ok so my device m21 updated to one ui 2.5 so as you know good lock app is not supported even if you install it using SAI then only two apps were supported nice catch and one hand operation.
There is an app Fine Lock which is in playstore but was not supported on my mobile So download a latest version of the apk from any website
Install Fine Lock using SAI Split Apk Installer download it from play store then open SAI and enable 'sign APKs' in settings then install fine lock using SAI After installing open Fine Lock and Click on any app you want to install it will open the fine lock website from there a list is given of all good lock apps click on whatever app you want to install (supported ones i have only downloaded 8 apps which i was sure they will work and they worked ) it will open the apk mirror page download the latest version and install the apk using SAI one by one and voila use fine lock to open them .
