F5 edge client for desktop windows 8

from the manual

• On the Main tab, click Access Policy > Secure Connectivity. A list of connectivity profiles displays.
• Select a connectivity profile.
• Click the Customize Package button. The Customize Windows Client Package popup screen displays with Available Components displayed. Most components are selected by default.
• Click Download. The screen closes and the package, BIGIPEdgeClient.exe, downloads.

thanks...

F5 Inbox EDGE Client is also included in Win8.1. It does not support all features but can be used easily.

https://support.f5.com/kb/en-us/products/big-ip_apm/releasenotes/related/config-note-f5-inbox-vpn-client-windows8.html?sr=47874003