Solution 1:

You are right, this utility is available for Ubuntu 20.10 and newer.

But you can simply download its deb-package to install on Ubuntu 20.04 manually with

cd ~/Downloads
wget http://archive.ubuntu.com/ubuntu/pool/universe/h/hcxtools/hcxtools_6.0.2-1_amd64.deb
sudo apt-get install ./hcxtools_6.0.2-1_amd64.deb

and then launch the utility by hcxpcaptool.

Solution 2:

hcxpcaptool was superceded by hcxpcapngtool. I think both were once available in hcxtools but now only the ng version is.

The new one seems to be mostly backwards compatible so you should be able to use it for whatever you needed hcxpcaptool.

In my case, after installing hcxtools, wifite was still complaining that hcxpcaptool was missing. I created this symlink to convince wifite that they're the same.

# ln -s /usr/local/bin/hcxpcapngtool /usr/local/bin/hcxpcaptool

Wifite was able to start after that, and perform PKMID captures. I doubt that the new tool is completely backwards compatible with the old one, so consider this a work-around and not a fix.