Yep.
Other than TestFlight, the only way to distribute iOS apps is through the App Store.
How will your iPhone/iPad users access their apps if you donโt go through the App Store @ajohnsbyfcqf?
Have you considered publishing your app as a web app? ๐ New Thunkable โ PRO Feature: Publish your Project as a Web App 2020-03-11
Would that be an option in your particular use case?