Thanks for the guide!
I link it from my recent blog post where I provide one new innovation: how to prevent the old app from updating.
I figured out this trick back in 2016, and I'm glad it still works.
- extract the .ipa
- locate the Payload folder
- open your iPhone in Apple Configurator
- drag the app from the Payload folder onto your iPhone
- done!
ps: an alternative page to get the build number is https://ipaarchive.com/app/usa/333903271 (sort by date)