How can we use autocomplete dropdown (select2) for filters in Django Admin for normal fields?

I used the django-admin-autocomplete-filter package but it seems to work only for the foreign keys.

Welcome @za7873 !

The package on PyPi by that name doesn’t appear to be well maintained - its last release was more than 3 years ago. Its issues list also shows a couple different problems being reported with more current versions of Django. (I see problems being reported under certain circumstances with both Django 4 and 5.)

Your desired use is also an identified issue - Support for non relational attribute filtering · Issue #49 · farhan0581/django-admin-autocomplete-filter · GitHub

So my best suggestion to you would be to fork the repo, add that support, and offer it back as a PR. Even if it’s not accepted, then you at least still have a version working as you need it to.