I haven’t had to deal with this specific kind of use case before (accessing the local Jellyfin service while the laptop is connected to a VPN), but after some cursory research, one of these approaches may work for you:

Easy Option (only available on some VPN software):

There may be an option in your VPN client that lets you access local network addresses like your Jellyfin server. Check your settings and see if there are any options like “allow local network traffic” and then try opening up your Jellyfin server in a browser (e.g.: http://192.168.1.100:8096/)

Less Easy Option:

If your VPN client doesn’t have an option for allowing local traffic, you can open up the command prompt on your macbook and run a command like this:

sudo route add -net 192.168.1.0/24 192.168.1.1

Where 192.168.1.0/24 is the local network you want to connect to (where the Jellyfin server is located), and 192.168.1.1 is your local gateway (probably your wifi router’s address). Change both of these depending on how your network’s local IPs are formatted.

This should update your routing table to handle local network addresses without the VPN and this should persist between reboots.

Hope this helps.