How to script Android 7.0 to enable Mobile Hotspot AND USB tethering upon startup?

You can use Tasker to accomplish this:

Objective: Auto Switch-on USB tethering and Mobile hotspot after boot

Profile (or Trigger)

Create a Profile which allows triggering of the Task at after boot:

• Go to Profiles Tab and click the "+"


• Event >> System >> Device Boot


• Tap back to exit from this window

Task

You will notice as soon as you exit, you will be prompted to link this Profile to a Task;

• Scroll all the way up the Task list select "New Task + "


• You can name this Task AutoTethering or anything.


• Click "+" to add new Action


• Code >> Run Shell [ Command: service call connectivity 33 i32 1, Tick "Use Root"]


• Tap back to exit from this task


• Click "+" to add another action


• Net >> WiFi Tether (Set On)


• Press back the way all back until you exit Tasker (your profiles are now saved and ready for execution)

Extras: Give Tasker more priority (allow auto-start for Tasker, exclude from battery optimisations, task killers etc)

Explanation: Soon after boot, the first action turns on USB tethering, and the second option
turns on WiFi tethering (note: there is no need for a second script because Tasker already
has a built in WiFi Tether variable which is capable of handling tethering state)

This should work. Cheers (tried and tested).