Dash mantine was update just two days ago, with the update a decent amount of changes where made but those changes haven’t been reflected in the documentation just yet so your bound to run into a range of issues when developing based off the newest version at this moment without a great amount of expertise in the dash-mantine-components and react-mantine-components libraries.
My suggestion is to downgrade the package with a pip install dash-mantine-components==0.12.1 or pip install dash-mantine-components==0.13.0a2, the code you’ve included will run just fine then and anything you build from referencing https://www.dash-mantine-components.com/ will work without problem.
If you really want to play around with the new 0.14.0 you can reference: Version v7.0.0 | Mantine as a bases for understanding the update thats taking place in this moment.