F-Droid no longer has up-to-date version
Latest VLC version available on F-Droid Archive is 2.5.9 : https://f-droid.org/wiki/page/org.videolan.vlc#2.5.9
Alternatively, providing a direct, fixed link to the latest version (e.g. here : https://www.videolan.org/vlc/download-android.html or here : https://get.videolan.org/vlc-android/) would allow the integration into other F-Droid repositories, such as IzzyOnDroid (https://apt.izzysoft.de/fdroid/)