There's not enough info from the source to go on, at least for me. I've done similar selects. Try this JS rule and see what happens:
setTimeout(function()
{
document.getElementById('mat-select-value-21').click();
document.getElementById('mat-option-1').click();
},1000);
If it works, but it's the wrong selection, change the number at the end of mat-option-1. For example: mat-option-2, etc.