Similar to Plex, you can use free software like Universal Media Server on your PC to stream files directly to the PS4 Media Player app. The PS4 acts as a DLNA renderer, picking up the stream from your computer.
For enthusiasts with a jailbroken console, is the only production-ready solution. Treat any standalone “VLC PKG” download link with extreme skepticism—if it sounds too good to be true on a forum from 2017, it probably is. vlc ps4 pkg
Another open-source project designed to play MKV and MP4 files directly from USB or hard drives on jailbroken consoles. Similar to Plex, you can use free software
: A dedicated homebrew media player often used as a more capable alternative to the stock app. Similar to Plex