Greetings!

This is interesting. I could see a clear reason for HeidiSQL, and maybe that leads to the reason for the others. I assume phpMyAdmin and Adminer are set up on the server while HeidiSQL is run remotely. If they’re all three remote, then my idea makes sense across all of them.

When you create a user in MySQL, you define a host. If you do not define a host, it defaults to localhost. This means that all users are “user@ip” and by default “user@localhost.” So when you try to log in externally, you’re not just logging in as “user” but as “user@yourexternalip” instead.

Creating a remote user works like this from the shell:

GRANT ALL PRIVILEGES ON database.* TO 'username'@'ipaddress' IDENTIFIED BY 'password';

To connect remotely, ipaddress should be your external IP as found here:
https://ifconfig.me/

Jarland