radio button default checked in angular code example
Example: angular 9 radio button checked
Try to specify value attributes. And do not forget that in case of radio buttons Model is not supposed to contain boolean value but should contain radio specific values like:
<input type="radio" name="food" value="beef" [(ngModel)]="myFood"> Beef
<input type="radio" name="food" value="lamb" [(ngModel)]="myFood"> Lamb
<input type="radio" name="food" value="fish" [(ngModel)]="myFood"> Fish