I am not sure if I responded previously in any of your tickets, so it's best to introduce myself -- my name is Ivan and I serve as the lead developer for everything kendo themes.
To cut to chase: initially, I suppose we are going to have a Bootstrap 5 themed swatch and as time progresses, we'll build our theme around it.
I 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 official release. (Time and time, we've dealt with breaking changes between RC).
There is one thing we can do for certain: eliminate said errors. Do you think you can attach a log, or a simple project that we can debug? Even if we don't have a full fledged bootstrap theme, I guess we can still play nicely with it.
Based on your log / project, I will add points of improvements in this public issue https://github.com/telerik/kendo-themes/issues/2154. You can follow the development of our Bootstrap v5 compatibility there and provide further feedback.
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