The issue was apiVersion, dependency conditions are working only on v2

apiVersion: v2
description: Core Helm Chart
name: test
version: 0.0.1
dependencies:
- name: core
  version: "0.5.4"
  repository: oci://123.dkr.ecr.eu-west-1.amazonaws.com

works as expected!

(leaving it for further "strugglers" here)