Curious to know what you mean by "old" USB keyboard. I am using the Bondi blue keyboard from ye olden days of the iMacs and have had no issues thus far. You might try unplugging and replugging, restarting (all the normal jazz).

Updates to SwiftUI and Charts will be coming in the Fall when iOS (etc) launches; it will be required to have that OS update in order to use those features. For example, if your app needs to support iOS 15, you would not be able to use the new Chart framework and would need to fall back to other methods of charting data.

I may have solved this by using LineMark's series property (as detailed here).

Poster Edit: The items to the right (red scribble) are listed in the sampleData_Future array.

I emailed Apple Support about this to change my username. I was told as of right now there is no ability to alter the usernames on the forum. 🫥