Does she use O365 PowerPoint? Because morph animations and similar stuff can’t be replicated with LO Impress properly.

You can run Jellyfin on the Ryzen 3600 machine and point it to the NAS movie directory. At least to try it out (Alternatively, throw some movie files on the machine locally as a test). Then just use the Jellyfin frontend (http://localhost:8096/) on the same machine as the media player. Then also try if you like using it via Jellyfin app on the phone

Only on Linux, because the HDMI forum didn’t allow AMD to write an open source driver with HDMI 2.1 features