truecharts/charts/stable/valheim/docs/installation_notes.md

Installation Notes

Valheim app does not support having different port numbers for port and targetPort. Setting port will set the same port number to targetPort and it's Environmental Variable. e.g Status HTTP Port, Supervisor HTTP Port, Server Port

Also, services named valheim1, valheim2, valheim3, should be continuous port numbers. eg 2456, 2457, 2458. You can't skip a number!