This may depend on the size of your library. I tried installing Jellyfin on a Synology NAS, which runs Plex just fine, and it ran so poorly it was basically unusable. It “worked”, but it was painful.
I thought it would be fine, because Plex has no issues, but it was painful. Every client I tried on the AppleTV was equally painful, and I didn't even try using a client until making sure all the metadata was downloaded and setup via the web UI. I was very deliberate and did one thing at a time, spending a whole day on it (mostly waiting and browsing to different screens to force metadata to get downloaded and cached).
With everyone saying Jellyfin can run on a Pi, I would think it would be better optimized for low-end hardware.
Edit: never mind, 2.5G is now the default, so you'll probably need more than 40 people to saturate that with streaming video.