> I used brew.sh to install Python, which I think uses the universal installer

As far as I know, Homebrew builds its own Python and Tk.

> After I reinstall macOS, if you need further testing, i’m open to trying.

Thanks. I think the next step would be to try to reproduce just using Tcl and Tk as this most likely is an issue in Tk rather than Python.  It's also quite possible that the underlying problem will be fixed in a future Monterey beta. Alas, I don't have time to look further into this in the immediate future.  Perhaps someone can follow up directly with the Tk folks.