I ended up using a hacky method, with some inspiration from @th8a:

wget https://github.com/agraef/purr-data/releases/download/2.9.0/pd-l2ork-2.9.0-ubuntu_16.04-x86_64.zip
unzip pd-l2ork-2.9.0-ubuntu_16.04-x86_64.zip
mkdir pd-l2ork-2.9.0-20190416-rev.2b3f27c-x86_64
dpkg-deb -R pd-l2ork-2.9.0-20190416-rev.2b3f27c-x86_64.deb pd-l2ork-2.9.0-20190416-rev.2b3f27c-x86_64
sed -i -e 's/libgsl2/libgsl23/g' pd-l2ork-2.9.0-20190416-rev.2b3f27c-x86_64/DEBIAN/control
sed -i -e 's/libpng12-0/libpng16-16/g' pd-l2ork-2.9.0-20190416-rev.2b3f27c-x86_64/DEBIAN/control
dpkg-deb -b pd-l2ork-2.9.0-20190416-rev.2b3f27c-x86_64 purrdata-pop.deb
sudo apt install ./purrdata-pop.deb

Seems to work ok with a lil testing, but I noticed fonts are a little funny in UI. Might be totally unrelated.

As a sidenote, when I usually have this problem (installing a deb I got off the internet) I can solve it 3 simple ways:

The simple method

double-click on the package file, and there is a little widget that comes up and lets you install it (and goes and finds the deps for you.)

The older, non-GUI method

sudo dpkg -i FILE.deb
# there will be errors
sudo apt-get -f install

This will grab all the deps (if they are available) and fix future apt errors.

The modern non-GUI method

You can also use the apt wrapper to do both steps:

sudo apt install ./FILE.deb

In most cases this works for things that are made for ubuntu, on Pop!OS, but in this case I get some errors (probly due to the version hard-coding):

sudo apt install ./pd-l2ork-2.9.0-20190416-rev.2b3f27c-x86_64.deb 
[sudo] password for konsumer: 
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Note, selecting 'pd-l2ork' instead of './pd-l2ork-2.9.0-20190416-rev.2b3f27c-x86_64.deb'
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 pd-l2ork : Depends: libgsl2 but it is not installable
            Depends: libpng12-0 (>= 1.2.13-4) but it is not installable
            Recommends: tap-plugins but it is not going to be installed
            Recommends: ladspa-foo-plugins but it is not going to be installed
            Recommends: invada-studio-plugins-ladspa but it is not going to be installed
            Recommends: blepvco but it is not going to be installed
            Recommends: swh-plugins but it is not going to be installed
            Recommends: mcp-plugins but it is not going to be installed
            Recommends: cmt but it is not going to be installed
            Recommends: blop but it is not going to be installed
            Recommends: slv2-jack but it is not installable
            Recommends: omins but it is not going to be installed
            Recommends: ubuntustudio-audio-plugins but it is not going to be installed
            Recommends: rev-plugins but it is not going to be installed
            Recommends: dssi-utils but it is not going to be installed
            Recommends: vco-plugins but it is not going to be installed
            Recommends: wah-plugins but it is not going to be installed
            Recommends: fil-plugins but it is not going to be installed
            Recommends: mda-lv2 but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

Is there a new one of these? I am having same problems (on Pop!OS) and that link appears dead.

It's not perfect, but here is a video of it working pretty well:

I am accomplishing something similar, in a different way, so I don't have to use full paths. Chek out pdpi. In MAIN.pd I dynamically load a patch like this:

When it receives a float message on programchange, it dynamically loads the patch, then sends a synthetic loadbang message (dynamic loaded stuff doesn't trigger loadbang.)

To wire things up, I have a catch~ L, catch~ R hooked to dac~ and s control, and s note hooked to ctlin and notein

I fixed it with a bang to step, which seems a bit hacky, but it works.

What are linked lists? I liked the idea of using the new text, as I am already using a fairly new vanilla. I built this arpeggiator with text objects. It seems to work much better, but there is still a pause when it loops around. Am I using text sequencer incorrectly, or is there a better way to use this?

Yeh, I was thinking I should combine the bang outlets by just inputting the current step (instead of a bang.) I suspected your advice, but I appreciate the confirmation. I will report back if I get it working.

I want to make an arpeggiator that tracks the current midi keys that are down and plays them in the order they were pressed, and removes them from the pattern when they are released. Basically loop through steps and play the current position in the list of current notes with makenote. I started trying to make this with list objects and it doesn't work well. Often keys stay "stuck" or will not register they were pressed. Is there a better way to accomplish this goal? Here is what I have. arp-help.pd is the example. Any suggestions on making it work are greatly appreciated.

I ended up using dynamic messages to load patches as objects. Seems to work really well. Here is my framework,