AppleTV is great but i don’t think any app would access a NAS filesystem directly
There are a couple these days – Infuse is very highly regarded, MrMC also seems quite popular. I couldn’t get either of them to work to my liking, particularly infuse with TV shows.
I have an apple TV, with plex media server loaded onto my Synology NAS. Works a treat. Apple TV has iPlayer/netflix/Prime video app etc…. the only things that are missing are 4OD and Spotify – but these are apparently in the works.
I had to upgrade the NAS as my previous one was 8 yrs old and so didn’t have enough chooch to run Plex Media server, and I didn’t want to have my laptop open any running any time Batfink Jnr wants to watch peppa pig/Cinderella.
I looked into buying a mini PC to run PMS, but ended up spending the money on a new NAS – which seemed like a better investment.
Really happy with the setup – although getting iTunes purchased content to play on plex is a bit of a faff!