Welcome to the community! Thank you for your question!
I’m taking the DHIS2 App Developer academy (we just finished the last live session today, actually) and yes we learned that to develop a web app, we need to use React.js to be able to develop a DHIS2 app.
There are many references and resources that could help you easily get started as a developer who already has experience in another language such as Vuejs. I’d like to invite you to watch the presentations from the DHIS2 App developer academy:
Thank you so much. I’ll definitely check out the links you shared.