backstage/.changeset/sour-rivers-fry.md

@backstage/create-app

@backstage/create-app
patch

Updated packages/app as well as the root package.json type resolutions to use React v18.

The @testing-library/* dependencies have also been updated to the ones compatible with React v18, and the test at packages/app/src/App.test.tsx had been updated to use more modern patterns that work better with these new versions.

For information on how to migrate existing apps to React v18, see the migration guide