Ok, I’ve updated the plugin to properly support the new emoji picker in Discourse 
It’s been tested in full and limited mode, and also on mobile. You can test it out here yourself:
https://try.thepavilion.io/t/heres-something-to-react-to/571
That site gets automatically rebuilt every 24 hours (which updates it to the latest Discourse). So if you’re on tests-passed (the default branch) it’s a good idea to test out any custom plugins you’re using there before you update.
I’ve also added a .discourse_compatibility file to the plugin:
Add .discourse_compatibility · gdpelican/retort@35aaad5 · GitHub.
This means that if you’re running the stable branch of Discourse you can keep updating as normal and this plugin will stay pinned at a commit that works with the latest stable release. See further here:
Introducing .discourse-compatibility: pinned plugin/theme versions for older Discourse versions.
In this case the last stable release of Discourse (2.5.1) was 2 weeks ago and the emoji-picker refactor that broke Retort was 10 days ago, so the stable commit for this plugin is Gobals are being loaded later · gdpelican/retort@92738f0 · GitHub which I made back in June (tested and working with stable 2.5.1).