I think since I wrote that last reply, I found out some more about this subject.  I had a couple clients who received substantial CLD's from the same stock -- Altaba.  Funny thing is, they also received them in 2019, and I'm not sure I reported them correctly.  Turns out Altaba is what Yahoo  turned into, after all they had left was some Alibaba stock that the predecessor AOL's CEO had thought might be a good idea.  (I might have this history wrong.)  Anyway, most investors probably recovered their basis, and then some, in 2019; by 2020 it was all LTCG.  On Schwab 1099's, no explanation was given.  On Merrill Lynch 1099's, the proceeds also showed up on the 1099-B sales reports, with basis (at least for one client) shown as zero.