I measure mine in this way:
- platform: command_line
name: CPU Temp
command: "cat /sys/class/thermal/thermal_zone0/temp"
unit_of_measurement: "°C"
value_template: "{{ value | multiply(0.001) | round(1) }}"
- platform: command_line
name: GPU Temp
command: "/opt/vc/bin/vcgencmd measure_temp"
unit_of_measurement: "°C"
value_template: '{{ value | regex_findall_index("=([0-9]*\.[0-9]*)", 0) }}'
- platform: command_line
name: CPU Clock
command: "/opt/vc/bin/vcgencmd measure_clock arm"
unit_of_measurement: "MHz"
value_template: '{{ value | regex_findall_index("=([0-9]*)", 0) | multiply(0.000001) | round(0) }}'