Running a recent Node version on DigitalOcean App platform

DigitalOcean App Platform apps by default currently (end 2023) run on Node 16.x, which is way too old for modern apps deployment.

To set a newer Node version, you have to change the buildpack of the App in the App Spec (you can do it in the app dashboard settings, after you deployed it for the first time):

features:
    - buildpack-stack=ubuntu-22

Then you set the version in your package.json:

{
  "engines": {
    "node": "21.x"
  }
}

(and for whatever reason, LTS versions are not supported, so I used 21.x)