Not true. I record to SD card these days, the only downside is no 4K (presumably due to speed limitations), but for 1080p 60 fps it works just fine.

You must get a top spec 64GB (larger capacities are too slow, smaller capacities have not enough space to record anything). Sigma publishes a list of known compatible SD cards.

If you suffer from the shadow flicker issue, let me know. I couldn’t truly enjoy fp until I worked around that.