If you tag your video
-tag:v hvc1
Your ffmpeg command works for me:
ffmpeg -framerate 60 -i %d.png -c:v libx265 -pix_fmt yuv420p -x265-params lossless=1 -vf scale=out_color_matrix=bt709 -color_primaries bt709 -color_trc bt709 -colorspace bt709 -tag:v hvc1 out.mov
I am using ffmpeg available from Conda-Forge at version; ffmpeg version 6.1.1
Edit: Looks like this does not preserve alpha transparency. In order to do so, I had to add/modify your list of arguments:
ffmpeg -framerate 60 \
-i %d.png \
-c:v hevc_videotoolbox \
-pix_fmt bgra \
-x265-params \
lossless=1 \
-vf scale=out_color_matrix=bt709 \
-color_primaries bt709 \
-color_trc bt709 \
-colorspace bt709 \
-alpha_quality 0.9 \
-tag:v hvc1 out.mov
hope this helps others!