Thanks David! Excellent pointers to Ubuntu 21.10! Will do that.
BTW, since this was my first posting, it was hidden for the weekend and just cleared today. In the meantime, your input and others in this related topic: https://forums.sifive.com/t/intermittent-kernel-oops-under-heavy-load/5009/13 has progressed further over the weekend.
So, I will move to track all actions on this issue to that other thread since it has more information than this one (mitigations, etc.).
Thanks for your help!