You can easily fly your Mavic Mini by using virtual reality goggles at DJI Fly application with no extra hardware or third part software.
Key step is choosing correct virtual reality goggles. Avoid more common double lens VR googles and look for a single lens FPV goggles.
I used this Hobbyking Quanum V2 Pro. Unfortunatelly they are now discontinued. You can try to find a similar item in the market, for example: 'Visor X Universal Smartphone 3D Glasses Screen Magnifier'.
If you prefer, another approach it as a DIY proyect, watch here: DIY 50$ FPV Goggles ! or search the web for 'How to make cheap FPV goggles'
Nice setup , but i believe this is technically illegal in my country because you need a direct visual line of sight of the drone and his surrounding. Well i will need to dig a little deeper to be sure ...
Anyway , even if it's allowed , i am not sure if i want to use FPV Goggles ... in my region i always need a clear view of the sky around my drone .. to much birds of prey circling and looking for a diner