how to always show homescreen after unlocking?
It seems that the only way to get this without automation is having the habit of pressing "show desktop" before locking.

In case, you are not against automation, you can accomplish your request with MacroDroid, Tasker or other apps.

With MacroDroid


In the Triggers section, select Screen Unlocked.
In the Actions section, select Launch Home Screen.
Give the macro a name, then save it.


When you unlock the screen, the home screen will be shown (there was about 300 ms delay when testing) even if another app was in the foreground.