If you are using #LibreNMS 26.3.1 on #FreeBSD please look at some real time port traffic.

Something like: device/device=120/tab=port/port=2411/view=realtime/

Does it graph for you?

If not, look at:

/usr/local/www/librenms/resources/views/graphs/realtime.blade.php

Change the first line to:

{{-- '<?xml version="1.0" encoding="UTF-8"?>' --}}

Does it work now?