Sequence Bitrise pipeline with Gitlab CI Step

How to sequence external (webhook triggered bitrise) and internal pipelines steps ?

Context

My project is an Android project
I use Bitrise for CI/CD
The Bitrise workflow is trigger thanks to a webhook

Final need

I want to publish coverage information into Gitlab mr

Probleme

The is no api to publish coverage report

Current workaround

The bitrise workflow will publish a downloadable artifact : the covertura coverage report
I expect/willing to trigger a step in gitlab at the end of the bitrise pipeline, to continue the job done by bitrise, and then download the report and push it to gitlab ongoing mr

How to do that ?

Here is a link in the bitrise Forum. but Bitrise thinks it is more a gitlab issue/question. https://discuss.bitrise.io/t/how-to-send-coverage-information-to-gitlab-mr/14483