I love what Purism is doing with its Librem phone, but I do not believe native Linux apps are a viable strategy. If Microsoft could not convince major app makers to support Windows Phone with its incredible UWP developer experience, I do not have hope for native Linux apps.
You might say, “I don’t need official apps. Those services have public APIs and I can build a Linux client.” Except for Twitter, I haven’t used a third-party app better than the official app. And many companies—like Fitbit—explicitly prohibit recreation of primary experiences.