On sails.js you need to use different libs to support newer versions of mongodb driver. There is an issue about it. As sails-mongo is not being updated, and won't work with mongodb 6.0.
I created a repo with the full solution: https://github.com/Goostavo/sails-mongodb-6
I'm using the following packages and files.
I'm also using configs for both standard host mongodb and serverless mongodb cluster on Atlas. When running on ATLAS i need to have some extra configuration, on datasets i use the config/env/ folders, and for sessions i made a crazy if/else loop to make the right connection string.
The configurations are set on a .env file or using ENVIRONMENT VARIABLES.
    "connect-mongodb-session": "^3.1.1",
    "sails-mongo-cloud": "^3.0.1",
File datastores.js:
/**
 * Datastores
 * (sails.config.datastores)
 */
let cfg = {
  host: 'localhost',
  port: 27017,
  database: process.env.MONGO_DATABASE || 'localDB'
};
module.exports.datastores = {
  default: {
    adapter: require('sails-mongo-cloud'),
    url: 'mongodb://' + cfg.host + ':' + cfg.port + '/' + cfg.database,
    socketTimeoutMS: 360000
  },
};
The session.js file:
/**
 * Session Configuration
 * (sails.config.session)
 *
 * Use the settings below to configure session integration in your app.
 * (for additional recommended settings, see `config/env/production.js`)
 *
 * For all available options, see:
 * https://sailsjs.com/config/session
 */
const cfg = {
  host: process.env.MONGO_HOST || 'localhost',
  port: process.env.MONGO_PORT || 27017,
  database: process.env.MONGO_DATABASE || 'localDB',
  user: process.env.MONGO_USER,
  password: process.env.MONGO_PWD,
  useatlas: process.env.USE_ATLAS
};
let url;
if (process.env.NODE_ENV === 'production' && cfg.useatlas) {
  url = 'mongodb+srv://' + cfg.user + ':' + cfg.password + '@' + cfg.host + '/' + cfg.database + '?retryWrites=true&w=majority';
} else if (process.env.NODE_ENV === 'production'){
  url = 'mongodb://' + cfg.user + ':' + cfg.password + '@' + cfg.host + '/' + cfg.database + '?retryWrites=true';
} else {
  if (!cfg.user) {
    url = 'mongodb://' + cfg.host + '/' + cfg.database + '?retryWrites=true';
  } else {
    url = 'mongodb://' + cfg.user + ':' + cfg.password + '@' + cfg.host + '/' + cfg.database + '?retryWrites=true';
  }
}
module.exports.session = {
  /***************************************************************************
  *                                                                          *
  * Session secret is automatically generated when your new app is created   *
  * Replace at your own risk in production-- you will invalidate the cookies *
  * of your users, forcing them to log in again.                             *
  *                                                                          *
  ***************************************************************************/
  secret: 'sails is awesome',
  /***************************************************************************
  *                                                                          *
  * Customize when built-in session support will be skipped.                 *
  *                                                                          *
  * (Useful for performance tuning; particularly to avoid wasting cycles on  *
  * session management when responding to simple requests for static assets, *
  * like images or stylesheets.)                                             *
  *                                                                          *
  * https://sailsjs.com/config/session                                       *
  *                                                                          *
  ***************************************************************************/
  cookie: {
    maxAge: 30 * 24 * 60 * 60 * 1000 // 30 days
  },
  adapter: 'connect-mongodb-session',
  'uri': url,
  //collection: 'sessions',
  // isSessionDisabled: function (req){
  //   return !!req.path.match(req._sails.LOOKS_LIKE_ASSET_RX);
  // },
  // isSessionDisabled: function (req){
  //   return !!req.path.match(req._sails.LOOKS_LIKE_ASSET_RX);
  // },
};