Microsoft has been fixing Windows 11's annoying white flash bug in File Explorer for over 2 years

The latest Windows 11 preview build mentions a fix for File Explorer that should stop it from flash banging you in dark mode.
TWCN Tech News

Preview Pane not working in File Explorer in Windows 11

Windows File Explorer offers a preview pane where, when a file is selected, a preview of the file content is displayed for some of the files. Text, PDF, and Images are some of them that support this.