Please tested with below command:
./ffmpeg -i ../fate-suite/mpeg2/t.mpg  -c:v prores_aw -color_primaries bt2020 -colorspace bt2020_ncl -color_trc smpte2084 -an output.mov

mediainfo outout.mov
...
Color primaries                          : BT.2020
Transfer characteristics                 : PQ
Matrix coefficients                      : BT.2020 non-constant

./ffmpeg -i ../fate-suite/mpeg2/t.mpg  -c:v prores_aw -color_primaries bt2020 -colorspace bt2020_ncl -color_trc arib-std-b67 -an output.mov
mediainfo outout.mov
...
Color primaries                          : BT.2020
Transfer characteristics                 : HLG
Matrix coefficients                      : BT.2020 non-constant
Signed-off-by: Limin Wang <lance.lmwang@gmail.com>