1. My Caddy version 2:
convert rules
RewriteRule ^index.php$ - [L]
add a trailing slash to /wp-admin
RewriteRule ^([_0-9a-zA-Z-]+/)?wp-admin$ $1wp-admin/ [R=301,L]
RewriteCond %{REQUEST_FILENAME} -f [OR]
RewriteCond %{REQUEST_FILENAME} -d
RewriteRule ^ - [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(wp-(content|admin|includes).) $2 [L]
RewriteRule ^([_0-9a-zA-Z-]+/)?(..php)$ $2 [L]
RewriteRule . index.php [L]
for caddy