The problem is a trailing comma in the esc_html__() function call with PHP<7.3.
A workaround for now is to remove the last comma in /wp-content/plugins/wp-security-audit-log/wp-security-audit-log.php on line 977
$result .= sprintf(
/* translators: 1: Plugin name. 2: Plugin name. 2: Freemius link. 4: Plugin name. */
esc_html__( 'Please help us improve %1$s! If you opt-in, some non-sensitive data about your usage of %2$s will be sent to %3$s, a diagnostic tracking service we use. If you skip this, that\'s okay! %2$s will still work just fine.', 'wp-security-audit-log' ) .
'<strong>' . $plugin_title . '</strong>',
'<strong>' . $plugin_title . '</strong>',
'<a href="https://wpactivitylog.com/support/kb/non-sensitive-diagnostic-data/" target="_blank" tabindex="1">freemius.com</a>',
'<strong>' . $plugin_title . '</strong>',
);
Remove the comma from the last line:
...
'<strong>' . $plugin_title . '</strong>'
);