Drupal 8.x

Update to 8.8.6 ends with "The website encountered an unexpected error. Please try again later." and this Message from Logs:

Drupal\Core\Extension\Exception\UnknownExtensionException: The module expandable_search does not exist. in Drupal\Core\Extension\ExtensionList->get()(Zeile 265 in core/lib/Drupal/Core/Extension/ExtensionList.php)

Doing an upgrade for the security path to 8.8.4 from 8.8.6. Doing this manually (delete core, vendor, *.* .[a-z]*) then tar the 8.8.6 file).  Run update.php and get the upgrade splash screen then the dreaded: "The website encountered an unexpected error. Please try again later."

/var/log/apache2/error.log has:

I am trying to create a restaurant website.  I have 2 slideshows configured in views.  One is a collection of beers and the other is a collection of food.  I put both slideshows in the content section as blocks.  No matter what I do, either with a twig file or css, I cannot get them to appear side by side.  They always show up one over the other.  What is the best way to display these side by side?

So I am working on building a site at dev.mydomain.com but after I will want to add it to mydomain.com without having to retype all my taxmonies and articles and extensions if possible is there a way to change the domain after I get it set up so I can make changes on our dev launch as I push content to our main site

I'm rebuilding a D7 module which allows my customer to build a secondary menu that changes depending on a node attribute. I've used the Menu API to dynamically create a custom menu. Using those custom menus, I've created MenuLinkContent successfully that are attached to them, but they don't appear on the page in the SecondaryMenuBlock I've assigned to the page.