Use external source bto trigger job pipeline

I use a self-managed GitLab Instance.

My GitLab CI/CD Pipeline triggers the execution of external programs A and B during the run of the pipeline. At some point of the run of the pipeline the pipeline depends on the status of the external programs (e.g. were the execution of the programs successful?).
So far I use the API of the external programs to pull the status the whole time. Instead of pulling the whole time the status, I want a push from the external programs to get notified when the runs of the external programs were successful.
The external programs are able to send notifications (POST request with a special payload including a lot of different information).

I need a feature/possiblity in GitLab to receive this POST request, which starts a job. Problem is, that the payload of the external programs cannot be customized.Normally I would like to use the generic alerts (, but this function expects the POST request in a special format. So the external programs and and generic alerts are not compatible. Is there a way that GitLab can process this special payload and triggers a job depending in the payload it gets?