There is probably a neater method but on my raspberry Pi I use Open media Vault as my file server. For a number of reasons but basically it makes the Rasp PI a NAS unit, which is great for sharing the media on various computers / TVs
You can use Emby server via the docker on OMV. Several YouTube instructions about using OMV / Docker / Emby server. To be honest I don’t use this route though. I’ve tried it and for what ever unknown reason I couldn’t get it to work.
So after setting up OMV as a NAS. I then logon into the Raspberry PI via the command line with SSH and use the following commands
Download server software
wget https://github.com/MediaBrowser/Emby.Releases/releases/download/4.0.2.0/emby-server-deb_4.0.2.0_armhf.deb
Install software package
dpkg -i emby-server-deb_4.0.1.0_armhf.deb
Remove previous download package
rm emby-server-deb_4.0.1.0_armhf.deb
Then it’s all up and running login to Emby server as normal.
Hope this is of some help