Update: this appears to be specific to the iOS simulator. So far I have not been able to reproduce the issue on actual hardware. So far I have been testing on an iPad running 13.2.3. I'm in the processing of updating it to 14 to see if that makes a difference.

Solved. And it was NOT specific to the Simulator. It's definitely a change from iOS 13 to iOS 14. The culprit turns out to have been a background thread spawned dispatched to set up an animation group. The setup function for the animation group was being run (for reasons I don't really understand) on a background utility thread. I fixed the issue by eliminating the dispatch to the background thread. The offending code was from the Swift Pulse library by Chris Tews. - https://github.com/ctews/SwiftPulse. I still find it odd that this never offended in previous versions of iOS. Apparently iOS 14 is a bit pickier or more observant.

Seriously, crickets? Surely someone else on this forum has experienced this. Another small issue: in the WkWebKit delegate the only thing we get back when the underlying webKit process dies is the webViewWebContentProcessDidTerminate call. No reason for the termination is given. Webkit has the reason code in the webContentProcessDidTerminateWithReason callback. Any chance that could be exposed in WkWebView? It would be nice to know why the process terminated.