It appears one or more impersonators have already registered some of the #Android applications that I maintained, including @appmanager. I've reported this to #Google, but not sure what's going to happen. The Android developer verification is still in beta, and it doesn't have a lot of features now to deal with this kind of problems.
Another issue is the 50% download requirements. Traditionally, most people would download the apps from #FDroid which historically used their own signing keys to sign the apps. Since most people have used #FDroid instead of other methods, only that signing key shows up there, and currently, it doesn't offer an option to choose a different key.
Also, since I do not have access to the signing keys used by F-Droid, it's effectively a dead-end. Taking down apps from F-Droid (and move to IzzyOnDroid completely) potentially forfeiting all the users who rely on updates from F-Droid.

Apps subjected to potential impersonation attack:
- App Manager
- Captive Portal Controller

Apps with F-Droid priorities:
- SetEdit
- UnApkm
- Metro (since this app is exclusive to F-Droid)

Today I've received the following generic-looking response from "Android developer verification support":
UPDATE: #Google seems to have fixed the issue anyway. I was able to register both App Manager and Captive Portal Controller in the Android developer verification console.
Google has added an “other ways to verify” option now. So, now it may be possible to bypass the 50% rule.