16 ERROR: process "/bin/bash -ol pipefail -c npm ci" did not complete successfully: exit code: 1

You are likely trying to run a development server on Railway since neither Ionic or Vite come with protection web servers.

https://github.com/railwayapp-templates/vue-starter (Its not an Ionic project but that doesn't matter)

Copy the nixpacks.toml and Caddyfile from this repo into yours, and if you have any build or start commands set in your service settings, remove them.

I am already using those files from the vue-starter kit.

To add a bit more detail, when i build locally, I'm using the following commands:
npm i --legacy-peer-deps
ionic serve

Any other suggestions?

My suggestion would be to fix the peer dependency issue.