Now, I finally can send SMS through the command line on an Android 8.0-oreo performing next steps:

 - Installing the ShellMS app on the phone (once for ever)
 - Going on the phone to Settings > Apps > ShellMS > Permissions > Enable all the permissions (once for ever). This step will no longer be necessary once an issue about permissions will be fixed
 - Connecting the phone to the computer with USB (and giving permission on the phone for accessing data, if asked)
 - Issuing next script on the computer:

<pre>#!/bin/bash
phonenumber="$1"
message="$2"
# escape double quotes
message=${message//\"/\\\"} 
adb shell "am startservice --user 0 -n com.android.shellms/.sendSMS -e contact \"$phonenumber\" -e msg \"$message\""
</pre>