This fork is working for me as long as it's paired with the Embed Module fork listed in this issue here 📌 Add CKEditor 5 compatibility and keep supporting CKEditor 4 RTBC (Just like in #68). It successfully solved an issue with a custom embed for the ckeditor 5 interface we were having. Wonderful work here folks.
Sorry I figured it out by making a new role rather than assigning it to an existing one. I still attached it to the admin role for anyone else who experiences this same error.
I'm a clown, I'll leave this open for you to close at your leisure. I'm unsure of the preferred method for a question that isn't a question anymore.
Chompp → created an issue.