Install Failed: Appex bundle at... does not define either an NSExtensionMainStoryBoard....

What's Wrong?

Running latest publicly available AltServer on Windows 10. Installation went perfectly fine (no errors) with my iPhone (iPhone X iOS 14.2), but fails on my other device (iPad Pro 10.5" Wi-Fi [iPad7,3] on iPadOS 14.2.
Received same error on Windows 10 as I did on a friend's Macbook, but only when I tried to use it on my iPad. Please see below for the contents of the error:

What device(s) & OS Version(s) are you using?

Windows 10 Pro with latest release of AltServer successfully installed.
Also tried on a MacBook with MacOS Catalina (I think, it didn't belong to me) with AltServer and Mail plugin both installed and running properly.

What have you tried so far to fix it?

On the MacBook, first I tried installing AltStore on my iPhone X on iOS 14.2 Successfully
On the MacBook, I tried to install AltStore on my iPad subsequently, and was given the error message listed below.
Thinking it may be a fluke, I tried again another 2 times with same result. Then I gave up and decided to try using a different computer:
On Windows, tested with iPhone X to ensure AltServer was working, which it seemed to be.
Next, tried my iPad Pro 10.5" (plugged it in, tapped 'trust,' made sure iCloud was running etc.) and was given the exact same error as when I attempted to install AltStore via the MacBook.

Error Message

Appex bundle at /var/installd/Library/Caches/com.apple.mobile.installd.staging/temp.OpoBeS/extracted/AltStore.app/PlugIns/AltWidgetExtension.appex with id com.N9L82UR2DV.com.rileytestut.AltStore.AltWidget does not define either an NSExtensionMainStoryboard or NSExtensionPrincipalClass key with a string value in the NSExtension dictionary in its Info.plist

Hopefully this format is acceptable! I've never submitted an issue before, so please let me know if there's any additional information that you might require.

No source files or tests are named. Start by reproducing the AltStore installation on the iPad Pro running iPadOS 14.2 and inspect the AltWidgetExtension.appex Info.plist referenced in the error; done means the extension installs successfully on the affected iPad while preserving the working iPhone installation.