I've just wanted to ask about this here and I figured it out after Googling the solution for a 100th time tonight.
I've had the following error pop up after I've migrated our Payload project to a spankin' new PNPM powered monorepo:
ERROR in ./src/payload.config.ts 17:13-20 Module not found: Error: Can't resolve 'process/browser' in 'C:\Working\codecrew\cms-monorepo\services\cms\src' ERROR in ./src/payload.config.ts Cannot read properties of undefined (reading 'module')
The solution was add the following package to the dependencies:
pnpm add--save-dev process