The .discourse-compatibility file was deleted from the repository when the styleguide plugin was moved into core, effectively removing the plugin from all installations, including those on stable. RGJ suggested restoring the file, but sam and joffreyjaffeux advised against it, citing potential issues and the upcoming stable release. Instead, they recommended using a forked version of the plugin for stable installations. RGJ clarified that their intention was to report the issue and prevent others from encountering it, not to implement a fix.
When the styleguide plugin was moved into core, the .discourse-compatibility file was deleted from the repository, effectively removing the plugin on all installations, including those on stable that do not incorporate the plugin.
I think it might be a good idea to restore that file
Yes given how close we are to the release you should try to make it work on your own hosting with a patch. Also I donβt expect many people to use styleguide, this was a very very niche plugin prior to it being added to core.
This was not about getting it to work on our own hosting (we already keep a repository of forks of all plugins for the stable branch), I was just reporting this because I still managed to bump my head and was trying to prevent others in encountering the same.