I can confirm the error reported by Pepe333 and DHQidiTech1 - it seems that the syntax has changed due to the new dual-extrusion logic.
I used to have (pre 3.5)
M104 S{material_print_temperature_layer_0}
and this output 210° in 3.5
I can confirm that changing this to (re. ahoeben's post above)
M104 S{material_print_temperature_layer_0, 0}
will now output the correct temperature (and not 210°).
The same is true for material_print_temperature.
Note: There is no syntax change for material_bed_temperatures