TypeError: Object.entries(...).flatMap is not a function

[cpursley]

Getting this when trying to run:

$ yarn dev
yarn run v1.22.5
warning package.json: No license field
$ next dev
ready - started server on http://localhost:3000
error - ./src/css/tailwind.css (./node_modules/css-loader/dist/cjs.js??ref--5-oneOf-6-1!./node_modules/next/dist/compiled/postcss-loader/cjs.js??ref--5-oneOf-6-2!./src/css/tailwind.css)
TypeError: Object.entries(...).flatMap is not a function
    at Array.forEach (<anonymous>)
Attention: Next.js now collects completely anonymous telemetry regarding usage.
This information is used to shape Next.js' roadmap and prioritize features.
You can learn more, including how to opt-out if you'd not like to participate in this anonymous program, by visiting the following URL:
https://nextjs.org/telemetry

event - build page: /next/dist/pages/_error
wait  - compiling...
error - ./src/css/tailwind.css (./node_modules/css-loader/dist/cjs.js??ref--5-oneOf-6-1!./node_modules/next/dist/compiled/postcss-loader/cjs.js??ref--5-oneOf-6-2!./src/css/tailwind.css)
TypeError: getProcessedPlugins is not a function
^C

[jakeprins]

Should be fixed if you use the latest node version locally. If you have installed nvm, try to switch to node 15 by running nvm use 15 and run yarn dev again