What's going to happen now that Huawei is releasing their new OS? If it blows up, and there's a good chance it will, there'd be a massive gap in access to a whole new platform. I've chosen the easy way out and I've been developing mobile apps for iOS and Android via React-Native. Will React-Native support HarmonyOS?
This question might be better directed towards the React Native Feature Requests page.
I haven't seen any mentions to add support for HarmonyOS at this stage, however the community could add support if there's demand. There's plenty of prior art around for alternative platforms.
If Facebook starts supporting HarmonyOS with its apps, then first-class support is much more likely.