It's an option given to you if the app is already in your purchase history for your AppleID. If not, then you have to find a newer device, sign in to it with your AppleID, download the app and then return to the old device and hope that a compatible older version is a) available and b) still functional and that the devs haven't turned off any server-side stuff that the older versions relied on.
Re:You're making me buy a new phone
by scarface74 on Tuesday March 28, 2023 @09:22AM
(#35340633)
You can still “buy” iOS apps on older (still available for download) versions of iTunes using the same Apple ID and then downloading an older version on your device.
This is not true and hasn’t been true since around the time that iOS 7 came out.
About two years ago, I dusted off an old first gen iPad (circa 2010). I reset it and I was able to download “the last compatible version”. It’s option given to you by the App Store. I was able to use Netflix, Hulu, Crackle, Spotify, Google Drive to read PDFs.