PDF's open in Edge for me. I us Brave for browsing and it can open PDF's but clicking on one in Explorer defaults to Edge I have to admit that I do kind-of miss Preview from MacOS.

If File Explorer Preview for PDF is not working or displaying correctly and shows ‘INDEX OF…’ under Network folders, here's what you need to do.

Rename it if you wish, and hit the Save button. On clicking the Save button, Microsoft Edge will download the PDF, and you can then open it later from File Explorer using your favorite PDF reader.

Reviews Review: 64-bit Adobe Preview Handler shows PDF thumbnails in Windows/File Explorer By Mark O'Neill Apr 4, 2013 2:00 pm PDT ...

Internet Explorer 11 has suffered an issue preventing PDFs from opening. Apps that use the 64-bit WebBrowser control suffered the same problem. The issue has now been addressed by Microsoft. In ...

XSS can be blocked in a managed network through filtering at a firewall or IDS/IPS. Individual users can disable PDF opening in their browsers. In Internet Explorer (since Microsoft Windows XP SP2 ...