Apps Script must be standalone for it to work with AppSheet?

[Bethel_Vasto]

Hello,

I have read tons on this topic and went through tutorials and posts, but I am stuck.

The official documentation says an Apps Script must be of the type standalone for it to be called by an AppSheet automation. But my standalone Apps Script doesn't have the option "from spreadsheet" for the installable trigger. I 've seen another user here asking the same question in a reply to a tutorial.

Just to make sure I didn't get the documentation wrong, I tried making my script container-bound, and in that case it won't show up in the list of Apps Script that are eligible to be called by an AppSheet automation.
Please help. 
TIA
@LeventK I went through your tutorial, thanks for taking the time to write it.  I am still confused though, because you talk about setting an onChange installable trigger from spreadsheet.

[Marc_Dillon]

If you're calling your script with a Bot, then you wouldn't need to install a "from spreadsheet" onChange trigger.

[Bethel_Vasto]

that's what I thought and that was my understanding from the official documentation, 
But since it wasn't working, I went through many posts to find a solution and found out that many users here advise installing a "from spreadsheet" onChange trigger.

[Bethel_Vasto]

such as this post https://www.googlecloudcommunity.com/gc/Tips-Tricks/Solved-Google-Script-and-Appsheet-integration/m-...

[Marc_Dillon]

Calling a GAS function directly from a Bot Task is a very new feature. Many of the threads you were reading were likely posted well before this feature was available.

[Bethel_Vasto]

Alright. Thanks. 
At this point I don't know where to look. My script works fine when manually executed from the editor, but it doesn't even get triggered when called from a Bot.