I finally bit the bullet and upgraded my websites to Drupal 8. For this website, the original was a bunch of static, hand-written html pages that hadn't been updated on over a decade, so this was more of an abandonment. My other site, Tony's Education Website, was a Drupal 6 site using a number of modules that had fallen out of maintenance. This is also my first serious go-around with Debian Jessie, and the notorious systemd. More about that in another post.
First the installation of Drupal 8 on the new machine. It failed. Got the "Configuration objects ... provided by standard have unmet dependencies" error. So I re-installed with the minimal configuration instead of standard. This worked, so I tried again with the standard config, which also worked. Man, I love non-deterministic computing!
Next I hit the RuntimeException: Guzzle requires cURL, the allow_url_fopen ini setting, or a custom HTTP handler. in GuzzleHttp\Client::getDefaultHandler() (line 125 of core/vendor/guzzlehttp/guzzle/src/Client.php). Fixed by installing the curl and guzzle php packages.
Finally, I was getting no text showing in a number of my nodes. Traced this down to the Missing filter plugin: filternull error in one of the content filters. Fixed this by modifying the filter, saving it and backing out the mod.
After that is was a matter of going through all the content. I had a bunch of pages that were using DruTeX that I had to change to use MathJAX, which was tedious rather than difficult, the only other issue was some pages being brought over as different types, probably because Drupal 6 was not as strict about it's html types, or there is not a strict 1-1 mapping.
The final annoying thing is ckeditor. The default config does not have undo-redo buttons! i mean seriously! It's also annoying that right-click brings up paste instead of spelling correction, so I have to switch to source view to fix my horrible typing.