how to disable a form control in the formbuilder in angular 9 code example

Example 1: how to set disabled flag formgroup angular

this.form.controls['name'].disable();

// or

<input formControlName="id" placeholder="ID" [attr.disabled]="true"></input>

Example 2: form changes button enable reactive forms

You can try it with the pristine property like this:
<button type="submit" [disabled]="form.pristine">Save</button>
This property checks if your form has changed since it was loaded.