What's the current procedure for getting the Kali template to work?

The Kali template is notoriously finicky, see e.g:

I have tried a number of solutions given in the various threads, but none of them appear to solve all the problems. The Kali template still appears broken and unable to update, and as a result, unable install software.

What is the current best practice for using the Kali template? Can it be used at all?

Try Distrobox Guide — Run Any Linux Distribution in Qubes Without Pain

You could try the template I build available at https://qubes.3isec.org
It’s built of Debian testing, and the Qubes packages for forky arent
yet available, except for those I build. I’ll be fixing this soon, so
official packages are available. That said, I use forky based qubes
almost all the time and all is good.

I got your template installed, and updated. Seems to work. But there doesn’t seem to be any way to install qubes-usb-proxy – did I miss something?

qubes-core-agent and other core Qubes tools are installed and available from the existing repos. But qubes-usb-proxy is not, and apt search qubes-usb-proxy returns no results. It might be possible to install it manually as per GitHub - QubesOS/qubes-app-linux-usb-proxy: USBIP over qrexec proxy · GitHub but that seems like a bad idea.

This page from 10 years ago seems to suggest qubes-usb-proxy is installable via repos for Kali. But it isn’t.

Is there a separate repo containing qubes-usb-proxy that I need to enable?