Did you use this solution on Whonix 16? The solution has incorrect lines and links to non-existent files.
scurl-download https://download.electrum.org/4.1.5/electrum-4.1.5-x86_64.AppImage.asc
gpg --verify electrum-4.1.5-x86_64.AppImage.asc
This address from the line and electrum-4.1.5-x86_64.AppImage.asc file does not exist.
I downloaded another asc from here. And I received this error on the verification:
gpg: no signed data
gpg: can't hash datafile: No data
Please check the solution and correct it if possible.
Did you use appimage on Whonix 16 and actual Electrum version?