Yeah, both Li-NMC and LiFePO4 can be damaged by charging when cell temps are below freezing. There is some anecdotal evidence that the very low C (current) rates we see with small panels could make it a non-issue. One of my nodes was up over last winter and froze a few times. I haven't observed any capacity reduction although TBF I didn't do any actual capacity tests.

In my campervan where I have a 380Ah LFP bank I use warming pads to keep the cells at human-comfortable temps.