I want to customise my phone to forward SMS messages automatically My goal is that I want to customise my own Android phone to automatically forward text messages from user defined phone numbers onto other user defined phone numbers. I tried updating a very simple app to do this:
https://github.com/EnixCoda/SMS-Forward
However I found that once I had updated to newer Android versions, the app started up and allowed me to set a forwarding number, but did not actually forward the SMS (I used my phone in USB debugger mode). The SMSReceiver class did not get the message that an SMS had arrived I found when I debugged it. I read more, and it seems that only the default SMS app is allowed to have anything to do with text messages. So now, I want to start from the source code of the stock/default SMS app that comes with Android so that I can add the features I am interested in to it.
I'm open to different approaches, but I don't want to download a crapware app with ads or pay nagging.
Doing a little more research, I found that Signal can handle SMS messages, but it seems like quite a big and complicated app.
Any advice appreciated!
You can try to create the following flow with Automate and test if it accomplishes it.

Create a new flow by pressing on the + button
Press again on the + button, search for SMS. Select &quot;SMS received&quot; block
Press the &quot;SMS received&quot; block. Enter the phone number of the sender. Click on &quot;Subscription ID&quot; and select your SIM card (Network provider). On the Message box, enter the name of a variable, for example msg. Click on Save.
Press the + button. Select the &quot;SMS send&quot; block. Press it. Enter the phone of the contact you want the SMS to. Set the Sim card (network provider) under &quot;Subscription Id&quot;. on the Message box, press on fx to enable it, then enter the variable create during step 3. In this case, enter msg. Click on Save
Link the blocks as seen on the first image below, then press back.
Give the flow a name and enable &quot;send and view messages&quot;. Give the requested permission, then press Start.

When an SMS is received from the sender whose number you entered on step 3, it will be immediately sent to the contact number entered in step 4. The log on the second image shows that an SMS was received then sent (forwarded).
Note: You should be able to add more number during step 3 and 4 by enabling fx. But I have not tested it. Or, you can add more SMS received and SMS send blocks in parallel for each number.
Disclaimer: I am just a user of the app.