PhpStorm Docker & zero-configuration Xdebug - php

Question

I am trying to set a zero-configuration debugging for PhpStorm/Docker/Xdebug.
Xdebug is installed properly (I can see it loaded on phpinfo()):
My PhpStorm setup for debugging is standard, listening on port 9000. Here is the xdebug config I'm using:
zend_extension=/usr/local/lib/php/extensions/no-debug-non-zts-20190902/xdebug.so
xdebug.remote_enable = 1
xdebug.remote_handler = dbgp
xdebug.remote_host = docker.for.mac.localhost
xdebug.remote_port = 9000
xdebug.remote_autostart = 1
xdebug.remote_connect_back = 0
xdebug.remote_log = /var/log/xdebug.log
xdebug.idekey = "PHPSTORM"
Off topic: I am also wondering if using xdebug.idekey is the same as providing IDE key through Chrome extension?
When I click on PhpStorm to start listening for connections, and set in the configuration to break on first line, I am getting the following:
Looking at Xdebug logs, it is clear that container connected to client (which is also clear from the fact that I am getting an error when trying to debug).
At this point, I have no manual servers or remote debug configurations set up.
If I define a server and remote debug configuration, and set environment key:
environment:
- PHP_IDE_CONFIG="serverName=docker-server"
And then if I click to debug:
Debugging then works, and no errors appear.
But this is then not a zero-configuration debugging...
What am I doing wrong?