Thanks! Indeed, I saw Changed the default command to `jupyter run`, but left in `execute` as an alias with a deprecation warning by palewire · Pull Request #173 · jupyter/nbclient · GitHub and didn’t look any further for followup or reverts. But jupyter execute is working as expected now, which is fantastic! 
(jupyter-run-debug) feickert@ThinkPad-X1:~/Code/debug/jupyter-run-debug$ jupyter execute debug.ipynb
[NbClientApp] Executing debug.ipynb
[NbClientApp] Executing notebook with kernel: python3