Unless VLC is one of the historic cases, F-Droid builds apps from source themselves [1]. They are more like a Linux Distro than an app store in that way. VLC hasn't had a new stable version tagged since 3.5.4 so that's what F-Droid ships[2].

[1]: https://f-droid.org/en/docs/FAQ_-_App_Developers/#will-my-ap... [2]: https://code.videolan.org/Skantes/vlc-android/-/blob/master/...