Here’s the sample proxy/echo service for `Iframely` to use with `@adobe/helix-fetch`. Put `CONFIG.PROXY_URL="http://<adress>:8089/proxy?url="` in your `Iframely` config to use this proxy.

logging.js

const moment = require('moment');

module.exports = function log() {
    var args = Array.prototype.slice.apply(arguments);
    args = args.filter(i => typeof i !== 'undefined' && i !== null);
    args.splice(0, 0, "--", "[" + moment().utc().format("YY-MM-DD HH:mm:ss") + "]");
    console.log.apply(console, args);
};

package.json

{
  "dependencies": {
    "@adobe/helix-fetch": "^3.0.0",
    "express": "^4.17.1",
    "moment": "^2.29.1"
  }
}

proxy.js

const { noCache } = require('@adobe/helix-fetch');
const express = require('express');
const app = express();
const log = require('./logging');

const port = 8089;

const fetch = noCache({
    h1: {
        keepAlive: true
    },
    rejectUnauthorized: false   // By default skip auth check for all.
}).fetch;

app.get('/proxy', function(req, res) {
    var url = req.query.url;
    if (!url) {
        res.status(400).send('"url" param required');
        return;
    }
    log('GET /proxy', url);
    const timer = new Date().getTime();
    const headers = Object.assign({}, req.headers);
    delete headers.connection;  // `connection` header is forbidden for `fetch`.
    delete headers.host;        // `host` is wrong to proxy.
    fetch(url, {
        headers: headers,
        redirect: 'manual',
    })
        .then(response => {
            const location = response.headers.get('location');
            var location_str;
            if (location) {
                location_str = 'redirect to: ' + location;
            }
            const duration = new Date().getTime() - timer;
            log('   response (in ' + duration + 'ms):', response.status, location_str, 'for:', url);
            res.status(response.status);
            const headers = response.headers.plain();
            delete headers['content-encoding']; // Remove 'gzip' and other encoding.            
            delete headers['content-length']; // Remove incorrect size for ungzipped.
            res.set(headers);
            response.body.pipe(res);
        })
        .catch(error => {
            log('   error:', error.message, 'for:', url);
            res.status(400).send('Error making request: ' + error.message);
        });
});

process.on('uncaughtException', function(err) {
    log(err.stack);
});
  
process.title = "proxy";

app.listen(port, () => {
    console.log(`App listening at http://localhost:${port}`);
});