Unable to configure Keystone 6 with MongoDB

I'm trying to set up Keystone using MongoDB as the database. Upon running keystone-next, the command errors out with the following error message: Error: Invalid db configuration. Please specify db.provider as either "sqlite" or "postgresql" at getDBProvider.

There's no much clarity on their docs on what values to pass as db.provider to use MongoDB as database.

Here are the contents of keystone.ts:

import { config, createSchema } from '@keystone-next/keystone/schema'
import 'dotenv/config'

const databaseUrl =
  process.env.DATABASE_URL || 'mongodb://localhost/keystone-project'

const sessionConfig = {
  maxAge: 60 * 60 * 24 * 90,
  secret: process.env.COOKIE_SECRET || 'keystone-project-secret'
}

export default config({
  server: {
    cors: {
      origin: [process.env.FRONTEND_URL],
      credentials: true
    }
  },
  db: {
    provider: 'mongoose',
    url: databaseUrl
    // TODO: add data seeding here
  },
  lists: createSchema({
    // Schema items go here
  }),
  ui: {
    // Change this for roles}
    isAccessAllowed: () => true
  }
  // Add session values here
})

Here are the project's dependencies from package.json:

{
...
"dependencies": {
    "@keystone-next/admin-ui": "^14.1.3",
    "@keystone-next/auth": "^31.0.0",
    "@keystone-next/cloudinary": "^6.0.6",
    "@keystone-next/fields": "^14.0.0",
    "@keystone-next/keystone": "^24.0.1",
    "@keystone-next/types": "^24.0.0",
    "@keystonejs/server-side-graphql-client": "^2.1.2",
    "@types/nodemailer": "^6.4.4",
    "dotenv": "^10.0.0",
    "next": "^11.1.0",
    "nodemailer": "^6.6.3",
    "react": "^17.0.2",
    "react-dom": "^17.0.2",
    "stripe": "^8.169.0"
  },
  "devDependencies": {
    "@babel/preset-env": "^7.15.4",
    "@babel/preset-react": "^7.14.5",
    "@babel/preset-typescript": "^7.15.0",
    "@types/node": "^16.7.10",
    "@typescript-eslint/eslint-plugin": "^4.29.2",
    "@typescript-eslint/parser": "^4.29.2",
    "babel-eslint": "^10.1.0",
    "eslint": "^7.32.0",
    "eslint-config-airbnb": "^18.2.1",
    "eslint-config-airbnb-typescript": "^12.3.1",
    "eslint-config-prettier": "^7.2.0",
    "eslint-plugin-html": "^6.1.2",
    "eslint-plugin-import": "^2.24.0",
    "eslint-plugin-jsx-a11y": "^6.4.1",
    "eslint-plugin-prettier": "^3.4.0",
    "eslint-plugin-react": "^7.24.0",
    "eslint-plugin-react-hooks": "^4.2.0",
    "prettier": "^2.3.2",
    "typescript": "^4.3.5"
  },
...
}

Keystone 6 (the version you're using here) doesn't yet support Mongo. You need to specify either PostgreSQL (postgresql) or SQLite (sqlite) as the DB provider.

Version 6 switched to using Prisma as the underlying ORM layer, giving the team a consistent way to access different DB platforms and letting us focus higher level functionality.

The Prisma team are working hard on adding Mongo support and the functionality was recently released as a preview. However some features (programmatic DB creation and some others I think) are blocking it's use with Keystone. PR #6102 tracks the progress on the Keystone side or #1277 over in the Prisma project. I can't offer and estimate on when this will land but it's being actively progressed.