Using stream-combiner2 with Gulp 4 - gulp

Question

I'm trying to use stream-combiner2 with my Gulp 4 task, as advised in the current version of this recipe. However, I always receive:
The following tasks did not complete: build:js
Did you forget to signal async completion?
I've read the excellent information in this answer about Gulp 4 async completion, but I'm having trouble applying that in my task. Here's what I have:
const browserify = require('browserify')
const buffer = require('vinyl-buffer')
const combiner = require('stream-combiner2')
const gulp = require('gulp')
const jsDest = 'static/js'
const jsPath = 'build/js'
const jsSrc = `${jsPath}/**/*.js`
const source = require('vinyl-source-stream')
const sourcemaps = require('gulp-sourcemaps')
const uglify = require('gulp-uglify')
gulp.task('build:js', function () {
const combined = combiner.obj([
browserify({
entries: `${jsPath}/main.js`,
debug: true
}),
source(`${jsPath}/main.js`),
buffer(),
sourcemaps.init({ loadMaps: true }),
uglify(),
sourcemaps.write('./'),
gulp.dest(jsDest)
])
combined.on('error', console.error.bind(console))
return combined
})

Answer 1

Somehow I missed this fantastic recipe for browserify with multiple sources and destinations. It allowed me to finally get what I was after, including well-formed error handling:
const browserify = require('browserify')
const buffer = require('gulp-buffer')
const combiner = require('stream-combiner2')
const gulp = require('gulp')
const gutil = require('gulp-util')
const jsDest = 'static/js'
const jsSrc = 'build/js/*.js'
const sourcemaps = require('gulp-sourcemaps')
const tap = require('gulp-tap')
const uglify = require('gulp-uglify')
gulp.task('build:js', function () {
const combined = combiner.obj([
gulp.src(jsSrc, { read: false }),
tap(function (file) {
gutil.log('bundling ' + file.path)
file.contents = browserify(file.path, { debug: true }).bundle()
}),
buffer(),
sourcemaps.init({ loadMaps: true }),
uglify(),
sourcemaps.write('./'),
gulp.dest(jsDest)
])
combined.on('error', console.error.bind(console))
return combined
})

Answer 2

After a few hours of hacking away at it, I got fed up with the task not doing what I want at all (see comments to the post) and resorted to the deprecated gulp-browserify. Here's the solution with that plugin, but I'm completely willing to accept an answer that can correctly incorporate stream-combiner2 with browserify itself, because that'd be much better.
const combiner = require('stream-combiner2')
const gulp = require('gulp')
const jsDest = 'static/js'
const jsSrc = 'build/js/*.js'
const sourcemaps = require('gulp-sourcemaps')
const uglify = require('gulp-uglify')
gulp.task('build:js', function () {
const combined = combiner.obj([
gulp.src(jsSrc),
sourcemaps.init(),
browserify(),
uglify(),
sourcemaps.write('.'),
gulp.dest(jsDest)
])
combined.on('error', console.error.bind(console))
return combined
})