Disabling Prototype.js breaks pages and plugins, which haven’t been migrated yet. I recommend taking a look at JENKINS-70906, tracking the progress.
If there’s no such issue tracking this task, please add one to the epic.
To make it even more precise, enabling the “Remove prototype.js” experiment without using an incremental build of the credentials plugin, the workflow-cps plugin, and the workflow-job plugin is unlikely to be a very good experience, since those plugins are likely used in the snippet generator and their Prototype.js pull requests have not yet been merged or released.
I’m using the following entries in my plugins.txt file to allow me to use incremental builds of the credentials plugins.
Are those plugins not maintained anymore? I would have assumed that such fundamental plugins (they look like core to me) would try to follow core changes in a very timely manner.
They are maintained, but the Prototype.js changes haven’t yet been merged and released. Prototype.js is still included in Jenkins core and should be included in Jenkins core until the widely used plugins have been released with the change to remove Prototype.js.