After upgrading the Ubuntu server from 1.16.40 to 1.16.100, I am seeing large lag spikes, far more regularly and with longer duration than ever before.  A few times per minute, players will lag for 2-4 seconds, after which the entities will either rapidly jump to their updated positions, or sometimes not move at all.  During the lag spikes, players cannot pick up items, attack mobs, or even open the inventory screen.

I haven't changed any aspects of the host machine or environment whatsoever between the before and after.  It must be some behavioral change in the new server version that's causing this.