Kaniko not able to auth against Nexus OSS

[JanHuege]

Actual behavior
Kaniko fails to auth against nexus while running in gitlab-ci

Kaniko-image: gcr.io/kaniko-project/executor:v1.14.0-debug
Nexus OSS Version: OSS 3.49.0-02

error checking push permissions -- make sure you entered the correct tag name, and that you are authenticated correctly, and try
again: checking push permission for "private.registry.com/repository/imagename:tag": creating push check transport for 
private.registry.com failed: GET https://private.registry.com/v2/: unexpected status code 404 Not Found: 
...[html]...

Expected behavior
Login should work. Docker login/push all works with v2

To Reproduce
Steps to reproduce the behavior:

1. Gitlab CI yml

    - echo "{\"auths\":{\"private.registry.com":{\"auth\":\"$NEXUS_DEPLOY_USER_PW_BASE64\"}}}" > /kaniko/.docker/config.json
    - /kaniko/executor
      --context "${CI_PROJECT_DIR}/frontend"
      --dockerfile "${CI_PROJECT_DIR}/frontend/Dockerfile.app-builder"
      --build-arg=CI_COMMIT_SHA=$CI_COMMIT_SHA
      --build-arg=CI_COMMIT_BRANCH=$CI_COMMIT_BRANCH
      --build-arg=CI_COMMIT_TAG=$CI_COMMIT_TAG
      --destination "$BASE_URL/app-ui:$APP_VERSION"
      --destination "$BASE_URL/app-ui:$BRANCH_TAG"
      --destination "$BASE_URL/app-ui"

2. run ci job
3. fails at 'checking push permission'

Triage Notes for the Maintainers

Description	Yes/No
Please check if this a new feature you are proposing
Please check if the build works in docker but not in kaniko
Please check if this error is seen when you use --cache flag
Please check if your dockerfile is a multistage dockerfile

[JanHuege]

Reproduction:

Dockerfile

FROM gcr.io/kaniko-project/executor:v1.14.0-debug

ADD Dockerfile.test Dockerfile.test

ARG REGISTRY_URL=[YOUR_NEXUS_URL]/repository/dockercontainer
ARG REGISTRY_USER=[your credential]
ARG REGISTRY_PASSWORD=[your credential]

RUN echo "{\"auths\":{\"$REGISTRY_URL\":{\"username\":\"$REGISTRY_USER\",\"password\":\"$REGISTRY_PASSWORD\"}}}" > /kaniko/.docker/config.json
RUN /kaniko/executor --context "." --dockerfile "Dockerfile.test" --destination "${REGISTRY_URL}/test:latest"
CMD [ "echo", "Hello World" ]

Dockerfile.test

FROM alpine:latest
CMD [ "echo", "Hello World" ]

Folderstructure

kaniko
  |__ Dockerfile
  |__ Dockerfile.test

Inside kaniko Folder:
docker build .

[JanHuege]

https://stackoverflow.com/questions/78278952/kaniko-not-able-to-auth-against-nexus-oss