How can I mirror audio and video from 2019 iMac to Fire Stick for free?

I am looking for a way to mirror streaming from my desktop to my fire stick as well as mirroring my music and photo library to the fire stick. Can this be done? How? Do you need an app? Is there a subscription cost?

I have tried AirScreen and it quit in the middle of a concert asking my to subscribe. Without a subscription, it would not let me continue.

Ieva