John,

Many times Ubuntu packages are not compatible with Debian packages (likewise Debian Packages may not be compatible with Ubuntu).
The versions of system files required are usually different, however as you know, it's technically possible and with a little bit of reasoning you can (hopefully) minimize the chance of breaking things.

This askubuntu.com page lists the corresponding version of Debian and Ubuntu: https://askubuntu.com/questions/445487/what-debian-version-are-the-different-ubuntu-versions-based-on
If you are on Debian Stretch (version 9) then you should look for packages build for Ubuntu Xenial (version 16.04) which is Ubuntu's long term support branch and most likely up-to-date.

NOTE: I don't recommend this :)

So here it goes:

Add

deb http://ppa.launchpad.net/dansmith/chirp-snapshots/ubuntu xenial main

to the end of /etc/apt/sources/list¶

Add Dan's signing key into apt

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys 837E6991DE70A952C07AE7176EA1BC913BC5163F

¶

Run

sudo apt update

¶

Run

sudo apt install chirp-daily

¶

Also NOTE:
That gpg/pgp key came from clicking on the "Technical details about this PPA" on the PPA landing page at https://launchpad.net/~dansmith/+archive/ubuntu/chirp-snapshots
You will see a shorter version of that gpg key in an error message from apt if you don't have that key marked as trusted.