Bought 2 about 4 years ago and had them paired at my work office. I have since retired and only kept one speaker, which I replaced with a table radio about 1 year ago.
It's in great condition and works as intended. There is no app anymore but you can set it/them up with your Android phone, see below...
From the Reva, Arena page online, they have instructions for apple products as well:
Android Device: Use Google Home App:
Log in (Required) will allow the user to setup and group Riva Arena and Festival speakers.
Select Devices at the bottom of the App.
Select the +Add button
Select "Google Nest or Partner device"
Choose/Create a home
Follow on-screen directions to complete Wi Fi setup of your Riva speaker
And here the AI description: