MacOS 15.3.1 (24D70)
Lookupper 1.3.2 (From the Mac App Store)
After installing Lookupper from the Mac App Store, It does not show me the onboarding screen where I could select a language. Instead it just shows the 'how to use' screen as shown below. I tried to make several different browsers the default to see if that was the issue, it didn't help.

Also, if I click Cmd+, (which would normally bring up the preferences window) it just shows me a blank window as shown below

Naturally because of the above issues, the actual functionality of Lookupper (viewing dictionary entries) doesn't work either