As others have mentioned, Jellyfin and Plex are good and pretty easy to setup. I prefer the minimalism of Jellyfin’s UI, but you’ll have more features with Plex, some features regardless of whether you want them. Emby is a similar option.

Those services running on your server will give you a nice interface and will handle the streaming from the server. You’ll need to do some setup to allow yourself to access the services on your home network either through a web GUI or the IP of your server via an app, and if you want to access the media remotely that will take a little more work to set up something like nginx proxy manager and a domain for remote access.

I recommend DB Tech’s videos on YouTube for guiding you through the process as a noob. His content is straight forward, just use the pause button if he’s moving too fast. He has been using OpenMediaVault for years (though just changed his setup) so his guides should line up quite a bit with what you’re doing.