When you say local files, do you mean files on a usb stick or hard drive plugged directly into the device?
I use Infuse on my Apple TV to access my videos on the network. It can pick up media from a samba share (or probably any other network share). There's more info on their site: https://firecore.com/infuse
It can also serve as a front end for a Plex server if you run that. While this isn't "local files", it works well and serves a similar purpose. Note: there is a very fair, cheap monthly/yearly/lifetime subscription required for any advanced features but it's free to try. I pay $12.99 for the yearly subscription and I'm incredibly satisfied. If this reads like an ad, it's not, I'm just really happy with it.
It can also serve as a front end for a Plex server if you run that. While this isn't "local files", it works well and serves a similar purpose. Note: there is a very fair, cheap monthly/yearly/lifetime subscription required for any advanced features but it's free to try. I pay $12.99 for the yearly subscription and I'm incredibly satisfied. If this reads like an ad, it's not, I'm just really happy with it.