The folder and file names of the IDLE open dialog is not visible because of absence of contrast (for example white on white).
Only clicking on the blank places where the names should be these become visible (because of selection background color) and curiously the clicked names remain visible even after these are no longer selected. Screenshots attached.

System:
OS: Linux Mint 21 Vanessa x86_64
Desktop: MATE 1.26.0
Python/Idle version: 3.10.6
Tk version: 8.6.12

Open Dialog:

Open Dialog After clicking on some blank places: