There’s a bug in Ubuntu 20.04.2 where sometimes installations end up without a kernel. That means you can’t boot them, which is a bit sad really.
We have identified a fix and we’re pushing it through the process now. Once it is validated, updated images will be reissued and we’ll post an announcement to the ubuntu-announce mailing list. That’ll be in a couple of days.
I just wanted to quickly post here to let you all know about this. If you’re affected by this, there is a workaround which is also given in the above linked bug - you can install with no network; disconnect WiFi and don’t plug in any network cable.
This affects all flavours which use the Ubiquity installer.
Sorry about this!