Could you please specify what exactly is not working when you use Typescript 3.9. Generally, the typescript definitions should have no issues, as long as the project where you use them is successfully build. That said no specific alignment or strategy from our side is applied against versioning of the TS. We do listen closely for reports and specific cases, as this might be the only aspect if something's wrong with the definitions.
As for the Chart, the typescript definition should not affect the behavior of the component in such a manner. That said, and having in mind the above-mentioned issue with the TS and Kendo, I would like to ask you to provide us with a runnable example where those issues reside. This way, we can inspect the entire implementation and pin down the reason for the issue.
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