@lseufer please elaborate on your problem and especially what value pin code can have.
How long is the pin code and can it contain letters and numbers at the same time?

Sorry about that.
It's 4 characters which can only be A, B, C or D.

Which model do you have? I am bit confused that you can only use those four letters instead of integers which are also used in the docs.

It's a wr143e. But the pin code is only of use on the keypad on the mower. Perhaps a pin code isn't required when communicating via the API. But as pin code is a required value for this integration, I can't try.

You could create a custom_component by copying all relevant files for this integration and changing the following line

vol.Required(CONF_PIN): cv.string,

This way you could test this integration with your wr143e.

I created the custom component but how do I make HA call it instead of the core one? I tried changing the name of the folder and of the sensor but to no avail. Sorry for the noob question.

You do not need to change the name of the folder or the sensor just keep everything as it is and change that one line. HA loads prioritzes custom components over built-in integrations so you do not have to do anything to call it instead of the core one.

It is still asking me for a pin and a numerical one. I did change line 24.

Have you restarted?

Yes. The config check did not let me so I even rebooted it but I am still getting The following integrations and platforms could not be set up:
sensor.worxlandroid
Please check your config.

Have you copied the entire folder and only made the change I suggested?
Here is the documentation reference on where HA is looking for integrations and how they are loaded https://developers.home-assistant.io/docs/creating_integration_file_structure#where-home-assistant-looks-for-integrations

That's what I did. I can now put 4 letters instead of numbers but the battery and state entities return "unknown" . Pin is however still mandatory, I can't remove it or leave it blank.

One possibility could be that your model is not supported. Moreover, you are correct it is still required since it uses it to do a basic authentication with your device. Not sure if it is possible without having the pin code.