How to configure my local Drupal site to contact my local Apache Solr server?
You haven't added any cores to Solr and you need to add at least one core and adjust the connection properties.

You will probably need the Solr 7 config from Search API Solr Search, as Apache Solr Search only has config for 5.x. The commands you need to run are: (replace CORE with the actual name)


cd /opt/solr/server/solr
sudo mkdir -p CORE/conf
sudo cp -R search_api_solr/solr-conf/7.x/* CORE/conf
cd /opt/solr
sudo -u solr ./bin/solr create -c CORE -d server/solr/CORE/conf


This should take the config files and create a core with those files. Then adjust your connection to http://localhost:8983/solr/CORE