Infuse for Apple TV will do this. You can point it to any folder on your NAS as an SMB share. It’s how I play back my own Blu-ray Discs, 4K or otherwise. It doesn’t do menus that I remember, but you can select the title easily enough.
Highly recommend also pointing it to your Jellyfin instance and using that as your front end for other files as it seems to me to have the best ability to do direct playback without transcoding, and the fewest hiccups for audio playback sync issues which can be annoying.
While you can just point Infuse directly at your other folders, its metadata cache gets dumped frequently by the OS, and it has to get rebuilt which is slow and annoying when you just want to watch something. Pointing at Jellyfin also lets you use whatever custom Jellyfin posters you’ve selected which helps for keeping special versions/collections identifiable visually.
Yeah that’s what I expected. I think the Kodi suggestion for the Shield is the most promising lead. Hope it works out.