Ubuntu on the VisionFive and the Nezha boards

On VisionFive board,
using Image: jammy-preinstalled-server-riscv64+visionfive.img,
Kernel: 5.17.0-1008-starfive

Attempting to install firefox
Output:
Package firefox is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

Also tried procedure listed here:
https://linuxiac.com/install-firefox-from-deb-on-ubuntu-22-04-lts/

Still shows no valid target package. Any ideas?

There doesn’t seem to be any built-in method of starting a browser, that I can see. The link on the XFCE desktop doesn’t work.