It's now documented here: https://www.angulararchitects.io/en/blog/testing-angular-standalone-components/

You can replace the standalone component with overrideComponent directly like this:

await TestBed.configureTestingModule({
  imports: [ AskComponent, HttpClientTestingModule]
})
  .overrideComponent(EditComponent, {
        remove: { imports: [EditComponent] },
        add: { imports: [EditStubComponent] },
  })
  .compileComponents();