I tried to use the git parameter plugin in a pipeline script to fill an input (Target Branch to merge to in another repository).
According to https://jenkins.io/doc/pipeline/steps/pipeline-input-step/ GitParameters should work for inputs,
This gets rendered but whatever I do the branch select stays empty (When refreshing I can see a brief spinner with "Retrieving..."). I also tried to capture related logs but couldn't get anything (From looking at the code only exceptional cases are logged).
I also tried as documented in https://jenkins.io/doc/pipeline/steps/pipeline-input-step/
Just to validate that it works in general I added the parameter to the job itself and if I trigger a parameterized build the select is properly filled.