(In reply to Alan W. Irwin from comment #26)
> Debian Jessie = oldstable had debug packages for libgl1-mesa-dri, but I
> can find nothing equivalent for Debian Stretch

Debugging symbol packages are in a separate repository now, add this to
/etc/apt/sources.list:

deb     https://deb.debian.org/debian-debug/    <suite>-debug   main contrib
non-free

(Replace <suite> with the suite name you have for the main repository there)

> Is there any further follow up you can recommend for the NMI-related error
> messages for the latest kernel lockup?

Looks e1000e network driver related.