I've long through someone could do well to use Chocolatey as the source of truth for a ConfigMgr metadata stream. The best alternative is MacUpdater, which is free. There are more than 50 alternatives to Patch My PC for a variety of platforms, including Windows, Linux, Online / Web-based, Mac and BSD. Chocolatey is the closest thing I know of but it's ConfigMgr integration isn't free/great. There are currently almost 100 third-party applications that Patch My PC can silently update' and is a popular software updater in the os & utilities category. There's some crowd-sourced community efforts ( CMPackager, RuckZuck, Chocolatey) out there that have been mentioned here but none of them have any kind of critical mass to support 100s of apps. To say nothing of the initial app install which in many cases require some amount of customization/configuration.

Further complicating matters is that not every org is going to want apps packaged with the same options. It's populating that stream with app data that is a tireless, never ending, grind that takes a high level of skill to do right. The cold-hard reality is that delivering a stream of 3rd party update metadata isn't that hard. Yea, there's no real 'free' alternative here.

Patchmypc