@Michael πΊπ¦ I apprciate your continued support but I am still at at a loss.
I have now pulled the stable friendica and addons from git and run composer.phar. For some reason, the latter required me to create /var/www/.cache and give write-permissions to www-data before it would work (my site sites in /var/www/html/friendica). As you see the instance is back running, I now see my addons (and have disabled them all for the time being). But I still get the 500 when trying to go to the admin panel.
How specifically do I use bin/console config to elicit a php error log in which I can see what is going on?