First, I would suggest your review of this post for an overview of the issues of integrating RPi with ROBOTIS CM-XXX controllers in general.
In that post, the CM-530 was used as the demo controller, but that post applies to the CM-550 as well. Among the videos listed there, there are some that pertain directly to RPi and CM-550 using Python or C++. If they do not contain enough details for you. You can check out this book written specifically for the CM-550 and RPi4B (and Jetson Nano).
https://www.amazon.com/Projects-Guide-ROBOTIS-ENGINEER-Combined-ebook/dp/B09KQCH2FV