Tried all versions from pre-1 to pre-3, similar errors appear… Unity version 2022.3.21f1
Library\PackageCache\com.unity.muse.common@1.0.0-pre.3\Runtime\UI\Controls\Canvas.cs(47,20): error CS0029: Cannot implicitly convert type ‘Unity.AppUI.Core.Optional<UnityEngine.Rect>’ to ‘UnityEngine.Rect’
Hi @iulia1393,
The current versions of Muse are not compatible with the new versions of AppUI. Can you try with an older version of the editor like 2022.3.20f1, or try to change the version of App UI to 1.0.0-pre.3 in your project manifest? You can verify after that in the Package manager that the correct version is installed. Sorry for the inconvenience 
"com.unity.dt.app-ui": "1.0.0-pre.3"
