I know we do not have support for Bootstrap 5 yet. Still, I'm trying to get charts to work, but I'm getting strange behavior.
We are going to have a Bootstrap 5 themed swatch and as time progresses, we'll build our theme around it. However, we can't give you an exact timeline yet, because we haven't yet planned it. Usually, we do not jump into beta products, because they might and usually do change. To us, a good version is an official release. (Time and time, we've dealt with breaking changes between RC).
Are you trying to render the Chart inside a Bootstrap 5 layout? Is it possible to share a Dojo demo of a sample implementation?