Thanks for the reply Darin but that doesn't work for me. In fact the guide I am using states specifically (link to that page)
that if you are using nginx then phpmyadmin will not work 'out of the box' - it says you need to add some directives under EACH SITE that requires phpmyadmin/squirrelmail to make it active.
But I found that real-world behaviour is actually very different as per my posts above.
Are you running nginx?
Anyway I managed to figure it out with a friend's help.
Note that my end goal was to have phpmyadmin/squirrelmail accesible by https://my.server.tld:8081/phpmyadmin
respectively, via https ONLY.
The resolution was to edit
To include the following 3 lines
And restart nginx. It now works.
Note that this is a self signed SSL Cert so obviouly it is better to replace it with a proper cert.