Build of Rails app on app platform fails early

Created an app using the app builder for my rails app. Then tried to deploy it, which resulted in a failure and this log…

[2022-05-18 11:17:49] => Initializing build
[2022-05-18 11:17:49] => Retrieving source code to /workspace
[2022-05-18 11:17:49] => Selecting branch "master"
[2022-05-18 11:18:05] => Checking out commit "da3767f507028ec29efcf4be7f478714cc4866f2"
[2022-05-18 11:18:11] => Got source_dir: /
[2022-05-18 11:18:11] => Using workspace root /workspace
[2022-05-18 11:18:11] 
[2022-05-18 11:18:11] => Building app using buildpacks
[2022-05-18 11:18:12] => Running buildpack detection
[2022-05-18 11:18:12] 
[2022-05-18 11:18:12] 4 of 5 buildpacks participating
[2022-05-18 11:18:12] heroku/nodejs-engine        0.5.1
[2022-05-18 11:18:12] heroku/ruby                 0.230.2
[2022-05-18 11:18:12] digitalocean/ruby-appdetect 0.0.2
[2022-05-18 11:18:12] digitalocean/procfile       0.0.3
[2022-05-18 11:18:12] 
[2022-05-18 11:18:12] For documentation on the buildpacks used to build your app, please see:
[2022-05-18 11:18:12]    Ruby: https://do.co/apps-buildpack-ruby
[2022-05-18 11:18:13] 
[2022-05-18 11:18:13] => Building app
[2022-05-18 11:18:13] 
[2022-05-18 11:18:13] ---> Node.js Buildpack
[2022-05-18 11:18:13] ---> Installing toolbox
[2022-05-18 11:18:13] ---> - jq
[2022-05-18 11:18:13] ---> - yj
[2022-05-18 11:18:15] ---> Getting Node version
[2022-05-18 11:18:15] ---> Resolving Node version
[2022-05-18 11:18:17] ERROR: failed to build: exit status 1
[2022-05-18 11:18:18] 
[2022-05-18 11:18:18] For documentation on the buildpacks used to build your app, please see:
[2022-05-18 11:18:18]    Ruby: https://do.co/apps-buildpack-ruby
[2022-05-18 11:18:18] 
[2022-05-18 11:18:18]  ! Build failed (145)
[]

Not very helpful :(

Can anyone tell me how to debug this?