It was possible to use Html in the Select button message up to R1 2023. The current behavior is a regression in R1 2023 SP2.
Dojo example: https://dojo.telerik.com/uyuhocUL
No actual Html can be used in the button's message.
Html can be used in other messages of the Upload, e.g., dropFilesHere, so it should be possible to do it in the Select button message as well.
I would like to request an example in the Kendo UI demonstrations which shows how to integrate the Kendo UI Upload with a Kendo UI Grid. It would also be nice to be able to submit files from selected files from the Grid using the Upload.