I tried upgrading next to canary (currently 14.2.0-26) to fix another issue, and it works in a linux environment (https://xpp7p5-3000.csb.app/) but it seems to be borked on Windows, throwing the following error:

Error evaluating Node.js code
Error: Failed to load external module (path)./postcss.config.js: Error [ERR_UNSUPPORTED_ESM_URL_SCHEME]: Only URLs with a scheme in: file, data, and node are supported by the default ESM loader. On Windows, absolute paths must be valid file:// URLs. Received protocol 'c:'