@T.Fly() Sorry for the troubles! In general the reported files shall be ignored, they exist only to be copied over the package.json file in the same directory when packing the alternative UPM package zip files spine.on-demand-loading 4.3-beta for spine-unity unitypackage from the download page here:
https://esotericsoftware.com/spine-unity-download#spine-unity-4.3-beta
These zip packages are intended to be used when not using Package Manager to install the spine-unity runtime but when it was installed via the spine-unity unitypackage (installed the "old way"). When you are installing the package via Install package from git URL.., these files should correctly be ignored. It's a pity that the latest version of the Unity Package Manager throws these error messages. In general you can safely ignore the error messages.
We will modify the directory structure or file naming so that the file is not causing any misleading error messages.