Custom Local Domains

How do you guys set internal domains?

Say i dont want to type 192.168.1.100:8096 and want a url instead, say jellyfin.servername - how would I go about that? I don't want it exposed online via reverse proxy. I don't need certs. No port forwarding on the router.

How do I type 'jellyfin.servername' into a browser and being up the jellyfin dashboard?