Audio speaker doesn’t work after recent update

Did you update wirelessly to iOS 16.4.1a ?

If yes, and to rule out a software issue, set your phone back to factory settings, using your computer.

Then set it up manually, without using the backup see if you can make phone use the ear-speaker.

Restore your iPhone, iPad, or iPod to factory settings - Apple Support

If this does not work, you should get the phone checked by visiting an Authorized Apple Service Provider.

Or, as this user in a related post did, make an appointment at the Genius Bar:

iPhone speakerphone doesn't work after up… - Apple Community

Did you already force restart your iPhone?

Force restart iPhone - Apple Support