wp-env fails in GitLab CI with “YIKES! It looks like you’re running this as root”

In some quick testing, I found that if I defined WP_CLI_ALLOW_ROOT=1 after I was already running as root, then WP CLI wouldn’t complain. I don’t know a lot about GitLab CI, unfortunately, but I’d try this to see if it works:

    image: docker:24.0.7

    services:
      - docker:24.0.7-dind

    variables:
      DOCKER_HOST: tcp://docker:2375
      DOCKER_TLS_CERTDIR: ""

    before_script:
      - apk add --no-cache nodejs npm git
      - npm install -g @wordpress/env

    stages:
      - test

    wp_env_test:
      stage: test
      script:
        - export WP_CLI_ALLOW_ROOT=1
        - wp-env start

…unless, of course, that’s what you already tried.