Most answers here are missing the benefits of a home Mac running 24/7 if you’re already part of the Apple ecosystem. For example, you can have it sync all your iCloud data (documents, photos, iTunes content) and back them up locally, then elsewhere outside of Apple’s ecosystem. You can also have it act as a local CDN for OS updates, whereby it will cache OS downloads locally so any subsequent updates will be super quick.
On the downside, I found native Docker on macOS kinda sucked, and just installed Ubuntu on my 2012 Mac Mini (now running Proxmox for funsies), but I have an old iMac to do the caching. You could probably virtualize and get both benefits, and I am considering moving to a new M4 mini for the power savings and sheer speed. That M4 Pro chip has absolutely incredible Geekbench numbers while sipping power.
You may want check out Infuse for the AppleTV. I have found it fixed every audio drift and video jitter concern that I’ve ever had with Plex or Jellyfin.
You can point it either directly at an SMB share, or a library hosted on Jellyfin or Plex. The advantage of this is it caches the artwork in the library, not on the AppleTV, because the AppleTV will periodically flush its local cache, leading to long re-fetching times and waiting to watch things.
I have no recommendations for the Chromecast.