The device was rooted with Magisk and the Termux app was installed. Every command is intended to be run as root.
ps -A
am help
Activity manager (activity) commands:
help
Print this help text.
start-activity ...
...
Not all the activies can be launched from the command line, e.g. the following
am start-activity app.lawnchair/com.android.quickstep.RecentsActivity
causes the Lawnchair app dies with a message on the screen Lawchair has stopped. Fortunately enough the app restarts automatically.
service -h
Usage: service [-h|-?]
service list
service check SERVICE
service call SERVICE CODE ...
Magisk modules are installed into /data/adb/modules/, each module is a subdirectory.