I think there is a misunderstanding. Lightroom is not included when subscribing to Adobe Express.
Here is a screenshot of the iOS listing for Adobe Express, specifically listing what the Premium Membership includes:
It is possible to use Lightroom Mobile for free. The app simply appears differently now, because deleted the free app (which does not sync) will not restore files that were inside the previous Lightroom app. Since the free app does not sync to cloud storage, the only way to recover images you previously had in Lightroom is to restore a device backup made at a point in time where you previously had Lightroom Mobile installed with images still inside the app. If you want to sync images in Lightroom to cloud storage from this point going forward, that will require a separate subscription to Lightroom.
If you have any further questions, please contact Adobe Support. Visit https://helpx.adobe.com/contact.html, sign in, and then select the chat option.