Chosen is not working on mobile devices?

Same issue here. Android with Chrome browser. Seems to work with tablet and larger screens.

It is indeed the case, the original chosen library is disabled on mobile devices:
https://github.com/harvesthq/chosen/pull/1388

I have not tested the new fork version in 4.x yet (https://packagist.org/packages/jjj/chosen)

Here's the link where this was discussed: https://www.drupal.org/project/chosen/issues/1338446 →