There is a note on the Joy UI Section of MUI.com wich states the development of Joy UI is currently on hold.

Joy UI is in beta and development is currently on hold. When starting a new project from scratch, we recommend Material UI over Joy UI because we can guarantee ongoing support.

Keep in mind that the maintainers are primarily focused on other projects and may not be able to respond in a timely manner to issues or pull requests related to Joy UI.