Thanks Ken, but I am after the actual App to install on my older iPad Air.
Because Apple no longer supports iOS 12, Sonos no longer fully support it either with their S2 App, at least not for system setup, or administration purposes.. you will find the current App will install and allow playback control and basic functionality only however … but for system setup and administration you need an iOS device with iOS 14, or higher, or an Android 8.0 device or higher etc.
MAC and PC controllers are in maintenance only mode and they too cannot be used for system setup/administration either.
Third party Apps are available but they’re for playback/control only too and cannot be used for setup/admin purposes - so you will need an App/Controller device that meets the requirements stated for actual system setup. Hope that assists.
You could look at setting up some of your products on S1 I guess (not recommended) as the requirements there are slightly less for that older type of setup and the products that are compatible are shown in the below link, but note (important) you will need to put your hands on an S1 only product to create an S1 system (it’s not possible to setup such a system with a device that is both S1/S2 compatible) and any devices run previously on S2 will need to be put through a Sonos downgrade process using the S2 App anyway on a compatible/supported iOS/Android device.
https://support.sonos.com/en-us/article/sonos-s2-compatibility