I have Opnsense OPNsense 25.7.11_2-amd64 installed on two different mini-pcs, on one the temperatures are clearly visible and posted inside a green box on the other the text is white on white background and barely visible, plus the temperature is way off (.1C). Should be near to 34 deg C since it is a fanless unit. I am using Opnsense-Dark theme on both units, they are different brands but both Intel based. Searches for the thermal sensor problem appear to be a little dated, I am using a current version of Opnsense so hopefully someone has an idea of a fix.--Thanks.
What sensor source are you using? "System: Settings: Miscellaneous" -> "Thermal Sensors". Sensors under FreeBSD are pretty limited; some devices export good ACPI data, some don't.