Ok now I got it, thanks for the help. Strange thing is that I could not add the parameters directly to the sensor but like that:
homeassistant:
customize_glob:
sensor.*_total:
last_reset: '1970-01-01T00:00:00+00:00'
state_class: measurement
Note that my relevant sensor names all end with “_total”, so if somebody wants to adopt that you should change your sensor names or the definition in the snipet above.