I'm typically an early adopter of new Ubuntu LTS releases and as such I reformatted my laptop with the release hoping to get going with .NET Core right away but the posted install guide on Microsoft docs didn't work. I went back to the docs a few days later and found that the guide had been pulled. After weeks of waiting we finally got an update today! The packages should be available on 5/12/2020 (only 2.5 weeks after the LTS dropped, 🎉 great job Microsoft!)
There are several workarounds for anyone that needs to use the SDK immediately. Check them out here.
UPDATE 5/13/2020: The Ubuntu packages are live and the dependencies issues yesterday were resolved. Here's how to get it going until Microsoft updates their documentation.
If you had previous failed attempts you may have to purge old sources.
sudo dpkg --purge packages-microsoft-prod && sudo dpkg -i packages-microsoft-prod.deb sudo apt-get update