Hello,
sorry for the late reply. Since version 11.19.0, PDF24 can do this: if PDF24 Reader is the default app for PDF files in Windows, File Explorer shows a preview of the first page instead of the PDF icon (in views that show thumbnails). If another program is the default app for PDF files, Windows does not use the PDF24 thumbnails.
So please:
- Install the current version of PDF24 Creator: https://tools.pdf24.org/en/creator
- Set PDF24 Reader as the default app for PDF files.