Cream According to the change log on GitHub, the spine-ue runtime in the 4.2-beta branch should already be compatible with Spine Editor 4.2-beta, but I just tried to see if I could open the example project on my end and got an error, and we just got a report from a user on GitHub that they also got an error, so it may not work properly at this time.
During the beta period, the editor side is updated very quickly and the runtime may not keep up with the editor updates, so if you try it and it does not work, please wait for a future runtime update.