The regression impact is properly documented && the plugin 2.1.4 is marked as incompatible, so it should minimize the impact on users. 2.1.3 is also available through archives.
Although I understand all the possible frustration by plugin users, I decided to NOT work on this issue. The regression has been introduced by me by a fix created during the working time, and I cordially apologize for any inconvenience it caused. Taking the proper regression announcement my team decided to not fix the regression in foreseeable future, because it is focused on other much more important tasks around Jenkins stability. I have no time to work on it during my spare time, because I am focused on the Jenkins core maintenance and other community work. On the other hand, I will be happy to review and deliver pull requests if somebody proposes them.
I would also like to highlight that the plugin is waiting for adoption for more than two years. During all this time I was trying to keep this plugin afloat by reviewing the incoming pull requests, fixing defects and keeping the codebase up to date to simplify the handover. But I have not been using this plugin on my own so that such maintenance was a bit lame. I invite all active users to contribute to the plugin by taking ownership of this plugin and of EnvInject API. I am happy to provide any required knowledge transfers and do some assistance during the first months of maintenance