Wanted to share something I found out about today when I was troubleshooting Jellyfin, hopefully it will help people out. Jellyfin wouldn’t connect when I had LAN Connections enabled on ProtonVPN, so I contacted support. They let me know that having Kill Switch enabled with LAN connection is incompatible:

"…the Killswitch and Allow LAN connections features are mutually exclusive due to their functionality differences, you will be unable to utilize both of them at the same time.

Unfortunately, due to compatibility issues within these features and some users experiencing issues when utilizing both of them, our team decided to make them mutually exclusive, therefore, at this moment you will not be able to utilize the Killswitch feature and have access to your LAN, therefore, if you wish to have access to your LAN, we suggest you keep the Killswitch feature disabled."

Not sure I understand how the two settings are related, but good to know! Another note is that Split Tunneling had no effect on this, so clearly Kill Switch also effects apps that are excluded in split tunneling also.