How to transfer data from webapp to addon – Telegram API

1. Project_1 is a container-bound script. A container is a readable spreadsheet (Template).

Code_1:

function doPost(e) {
  return HtmlService.createHtmlOutput(JSON.stringify(e));
}

The user makes a copy of the Template, deploys the script (Project_1) as a webapp with permissions: "Execute as: Me, Who has access: Anyone". The user is the owner of Project_1.

2. Project_2 is a script deployed as an add-on. The user from point 1 is not the owner of Project_2.

Code_2:

function sendPost() {
  var sheetURL = SpreadsheetApp.getActiveSpreadsheet().getUrl();

  var webAppUrl = "https://script.google.com/macros/s/###/exec"; // 7: Part_1 - WebApp: Tester

  // var auth = ScriptApp.getOAuthToken();
  // var header = { 'Authorization': 'Bearer ' + auth };
  var payload = { scriptName: 'updateData', sheetURL: 'sheetURL' };
  var options = {
    method: 'post',
    // headers: header,
    muteHttpExceptions: true,
    payload: payload
  };

  var resp = UrlFetchApp.fetch(webAppUrl, options);
  var respTxt = resp.getContentText();
  console.log('resp: ' + respTxt);
}

function doPost(ev) {
  var respWebapp = func(ev);
}

The user installs an add-on (Project_2).

3. The flow in the direction of addon -> webapp is fine: when sendPost() starts, it sends a request to the webapp and receives a response with the necessary data_1 in response.

The flow in the direction of "someone on the web" -> webapp also flows well: when requesting a webapp_url receives the transferred data_2.

4. I am trying to transfer data_2 to an addon.
   I read a lot about scripts.run, but it seems that this option is not applicable in such a situation.
   There is also nowhere to add an eventListener.

5. I would not want to deploy webapp from my account, so as not to spend my quota for simultaneous executions (<= 30).
   Also I would not like to do a sidebar, etc. in the spreadsheet and try to screw eventListener to html. I assume that with this approach, the listener (if it is possible to add it there at all) will be active only when ui is active (the spreadsheet is open and the sidebar is active). Data can come at any time of the day and must be immediately transferred to the addon.

Added:
I feel like I’m stumped. Therefore I reaches out to the community in the hope that someone would suggest a workaround or a new strategy for this initial data. By initial data I mean provide the opportunity for more than 30 users to exchange messages in both directions Spreadsheet <–> External service (for example, Telegram) and at the same time not fall under the limit of 30 simultaneous script executions.

Added_2:
I’m going to assign a bounty, so I’m transferring here from the comments what is missing in the post and updating the question itself.

I rejected the option with immediate entry into the sheet, because this will cause constant calls to the spreadsheet and slow down the performance of the system as a whole.

I am aware of the existence of Google cloud functions and Google compute engine, but would like to stay within the free quotas.

QUESTION: How to transfer data from webapp to addon and execute func () or which workaround to use to achieve the goals?