For closed source repositories of software that is currently available it's just a matter of having them included by default and actively prompting them on app managers as opposed to defaulting to hiding anything that isn't open source by default. Different distros come closer or further from this in the first place.

I imagine if you were going to go out of your way a bit further you'd restructure some of your splash pages and manager layouts to promote those based on popularity out of the gate.

There's an argument for a next step to be pre-packaging windows apps that can work under Wine directly in a package manager, but that's a bigger project and I genuinely don't think Wine is ready for that yet. Linux probably needs a better translation layer that works more reliably and comprehensively before that's an option. But hey, somebody should get on all of that, too.