A presentation on the current state of the near-RT RIC with a developer-level introduction on how to develop an xApp was given at the Open Source Conference 2021 (5G, IoT and Edge Computing) (organized by the IEEE ComSoc Bangalore chapter and Samsung SOSCON): slides: part 1 (intro to OSC and near-RT RIC) and part 2 (developing an xApp) and video link
A presentation on the new additions in Cherry as well as on some work on xApp side we gave at the virtual ONeS 2020: link (scroll down to the PDF) or video: link
For now you can get a good overview from this presentation at the ONS (Open Networking Summit), Antwerpen, 2019: Near_RT_RIC_for_ONS (PDF)