You can download a database with 40k movies here: https://radarr.video/dev/radarr.db (Version where the next refresh movie scan is in a year. The refresh movie scan will lag the UI and other stuff. https://radarr.video/dev/radarr_no_scan.db). Just place it in your AppData Directory while Radarr is not running and make sure it's named radarr.db (https://github.com/Radarr/Radarr/wiki/AppData-Directory).
You will have to message me (@galli-leo) via Discord or Reddit for the username and password (just as a precaution).
The actual tasks that are not related to the foundation of the new UI are all listed here https://github.com/Radarr/Radarr/projects/4. They are sorted according to different priorities. Some issues are also issues that shouldn't need anything extra, just a correct implementation in the new UI.