Is there a way to downgrade an app and keep the app data you have built up by using the newer version of the app (e.g. keep game scores, keep wifi test history, etc...)
If you have the app binary IPA cached and ready to install, yes you can try that by wiping the device, reload the data and only restore the app version you control.
This is not something that’s been easy or even possible for most people without prior setup work in the past few years as iTunes no longer manages local IPA downloads.
- ground control might work if you’re already using that
- Apple configurator might be able to help if you already use it
In almost all cases, the answer is no. Even if you’re a dedicated IT department, you will need to plan to prevent upgrades until you test things as opposed to have a roll back option.
App upgrade and installation is one way forward by very intentional design. Work with the vendor to fix your issue in the next build or choose to not use the app are the practical choices for the vast majority of cases.