How to install Good Lock in M21

You can install using SAI(SPLIT APK INSTALLER).
But modules doesn't work.
You have to wait for One UI 4.0.
Samsung may make it available with One UI 4.0.
Not sure about it.

Right now not possible

Not available officially currently, but we can increase chances of getting it in next major os upgrade by,
Provide feedback to samsung developers via feedback section(ask questions section), they need a minimum no. Of feedback from unique users (respect to no. of sales of device across all platforms), to add a premium feature. To provide feedback in samsung members app, Open Samsung Members Application > Get help > Send Feedback > Ask questions. If you want quicker action, write on every channel, whatsapp, samsung members app - ask question and error report, ceo escalation desk, service head desk, call toll free no. , support email of samsung, youtube, samsung content help( google it),samsung live chat,twitter, instagram,facebook,linkedin,etc. It is the power of our feedbacks only , that samsung started to give clipboard in many devices.

Continue giving, we got clipboard and samsung pay mini, we also take ca from Samsung.

Also, sign this petition
http://change.org/WeWantBasicFeatures