I took inspiration from Understanding Permissions for the Caddy server - #2 by Whitestrake
… And ran the following commands:
$ sudo chown -R <myuser>:www-data /var/www/wordpress
$ sudo find /var/www/wordpress -type d -exec chmod ug+rwx {} \;
$ sudo find /var/www/wordpress -type f -exec chmod ug+rw {} \;
$ sudo find /var/www/wordpress -type d -exec chmod g+s {} \;
Permissions now read:
$ sudo ls -l /var/www/wordpress
total 228
-rwxrwx--- 1 myuser www-data 405 Feb 6 2020 index.php
-rwxrwx--- 1 myuser www-data 19915 Jan 1 2023 license.txt
-rwxrwx--- 1 myuser www-data 7399 Jul 5 18:41 readme.html
-rwxrwx--- 1 myuser www-data 7211 May 12 2023 wp-activate.php
drwxrws--- 9 myuser www-data 4096 Dec 6 16:25 wp-admin
-rwxrwx--- 1 myuser www-data 351 Feb 6 2020 wp-blog-header.php
-rwxrwx--- 1 myuser www-data 2323 Jun 14 2023 wp-comments-post.php
-rwxrwx--- 1 myuser www-data 3013 Nov 15 17:47 wp-config-sample.php
drwxrws--- 4 myuser www-data 4096 Dec 6 16:25 wp-content
-rwxrwx--- 1 myuser www-data 5638 May 30 2023 wp-cron.php
drwxrws--- 27 myuser www-data 12288 Dec 6 16:25 wp-includes
-rwxrwx--- 1 myuser www-data 2502 Nov 26 2022 wp-links-opml.php
-rwxrwx--- 1 myuser www-data 3927 Jul 16 13:16 wp-load.php
-rwxrwx--- 1 myuser www-data 50924 Sep 29 23:01 wp-login.php
-rwxrwx--- 1 myuser www-data 8525 Sep 16 07:50 wp-mail.php
-rwxrwx--- 1 myuser www-data 26409 Oct 10 15:05 wp-settings.php
-rwxrwx--- 1 myuser www-data 34385 Jun 19 2023 wp-signup.php
-rwxrwx--- 1 myuser www-data 4885 Jun 22 2023 wp-trackback.php
-rwxrwx--- 1 myuser www-data 3154 Sep 30 08:39 xmlrpc.php
After a sudo systemctl restart caddy the 403 error persists. Any help would be greatly appreciated.