Answer by Simon_Weaver for Trigger matAutocomplete programmatically

You can also read the trigger from the <input> field explicitly like this - which may be necessary if you have multiple search fields.

<input #searchAutocompleteTrigger="matAutocompleteTrigger" .../>

Then read the viewChild

// using the new signal based viewChildsearchAutocompleteTrigger = viewChild.required<MatAutocompleteTrigger>('searchAutocompleteTrigger');// traditional @ViewChild    @ViewChild('searchAutocompleteTrigger', { read: MatAutocompleteTrigger }) searchAutocompleteTrigger!: MatAutocompleteTrigger;