Did I not make this very clear?
There is no longer a way to download DIRECTLY apps to an older device running an older iOS when the app has moved onto a newer iOS version.
The ONLY way to do this is to use either of the two procedures I have meticulously outlined and provided.
To be able to download an older version of an app to an older iPad, you either have to install the current version of an app first to a newer iDevice or download the current version of an app to iTunes on a computer.
Then you can go back to your older iPad and older iOS and then re-try downloading an older version of the app from the iOS App Store from your older iPad.
Only older versions of iTunes still support storing apps and iDevice screen page app layouts.
Newer versions of iTunes did away with iDevice app support.
So, you need to download and use an older of iTunes ( iTunes 12.6.5 or earlier ) so you can download current iOS Apps to iTunes, from the iOS App Store through iTunes, before you can attempt to download older versions of apps from your older iPad using the iOS App Store on that older iPad.
These two methods ARE THE ONLY WAY you are going to get older versions of apps onto your older iPad at this stage.
No other options.
These procedures work.
Carefully read and follow either procedure.
I put in the Web browser updating note as a courtesy to users still using older iPad models, running iOS 9 or earlier, to install and use a more current supported and up to date and more secure Web browser for their older iPads.
Good Luck to You!