The problem:
eslint-plugin-react version in your project’s dependency is “different” from the one in eslint-config-react-app package’s dependency, hence “conflicting”.
The solution:
Avoid deleting the .lock file as many suggested here (it’s there for a reason). Instead, dedupe its entries and then re-install.
npm:
npm dedupe && npm i
yarn v1:
npx yarn-deduplicate && yarn
yarn v3+:
yarn dedupe
pnpm:
pnpm dlx pnpm-deduplicate && pnpm i