Hi and welcome to Serverbuilds!
You are going to have trouble finding server parts based on the AM4 platform. There was not very much produced as it wasn’t really a market segment in enterprise. AM4 servers were really more of a novelty.
For your use case I would look at the Intel platform as you get Quick Sync Video (QSV) for video transcoding and many more options in terms of workstation / low end server components. The current sweet spot for price / performance is Intels 8th / 9th Gen which support DDR4 memory and have a fairly modern version of QSV and are old enough that you can find used parts fairly cheaply. I recommend you check out the NK 6.0 Build Guide
The parts you currently have are fine pieces of silicon, but would probably be better suited to a Workstation / Gaming PC. I would recommend using them for another build or selling them and putting the money towards building something more like the NK 6 which will be better suited for a home media server.