How to verify your Ubuntu download

Could you please provide alternate steps to obtain the public GPG keys which don’t rely on “hkp://”? My organisation’s proxy only allows me http/https access to the internet.

The specific command I need to work around is:
gpg --keyid-format long --keyserver hkp://keyserver.ubuntu.com --recv-keys 0x46181433FBB75451 0xD94AA3F0EFE21092

Thank you!