OnSong is a universal iOS and iPadOS app that supports iOS 15 and newer.
Recommended Devices
Please refer to Apple's list of compatible devices for iOS and iPadOS 15:
iPadOS: https://support.apple.com/guide/ipad/supported-models-ipad213a25b2/15.0/ipados/15.0
Upgrade Path
The good news is that iPads cost less than ever for significant performance and capability. You can purchase a new iPad for around $300 that will provide great value for a tool you can use for years. Check out this link to view these iPads.