Minecraft app : I bought it via the App Lounge but then it doesn't work on /e/ os! :(

Not really so much a hack if one is rooted. There is a Magisk module that replaces FakeStore (now known as App Lounge Store on /e/) with the patched Play Store from Nanolx. No other Google services need be installed or hacked around.
Otherwise yeah, the hacky way by manually replacing and pushing files. Consulting the installer contents might give ideas.

[MODULE] fakestore2playstore - microG with License Verification + In-App-Purchases | XDA Forums

Previously memtioned in this thread

Note that latest version of module is 0.2 from the GitHub.