I'm relatively new to web development, and I've set up a self-hosted (LAMP) WP site. After one too many configuration changes I broke the site. Apache error logs are clear as to where and when things went wrong, but I'm not sure how to correct the issue.
Any input on what the next troubleshooting steps would be?
Error Log:
[Wed Sep 14 09:28:38.141063 2022] [php:warn] [pid 38822] [client 173.68.17.120:49300] PHP Warning: Attempt to read property "post_type" on null in /var/www/liquidmodernlife.ddns.net/wp-content/plugins/wordpress-seo/src/integrations/third-party/elementor.php on line 154, referer: https://liquidmodernlife.ddns.net/wp-admin/post.php?post=541&action=elementor
sh: 1: /usr/sbin/sendmail: not found
[Wed Sep 14 21:21:25.401592 2022] [mpm_prefork:notice] [pid 1152] AH00170: caught SIGWINCH, shutting down gracefully
[Wed Sep 14 21:23:27.243231 2022] [mpm_prefork:notice] [pid 1196] AH00163: Apache/2.4.52 (Ubuntu) OpenSSL/3.0.2 configured -- resuming normal operations
[Wed Sep 14 21:23:27.329219 2022] [core:notice] [pid 1196] AH00094: Command line: '/usr/sbin/apache2'
sh: 1: /usr/sbin/sendmail: not found
[Thu Sep 15 00:00:33.180904 2022] [mpm_prefork:notice] [pid 1196] AH00171: Graceful restart requested, doing restart AH00558: apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1. Set the 'ServerName' directive globally to suppress this message