Thanks for reporting this issue!
PureOS is generally based on Debian: Package in Debian without issues flow directly into PureOS.
A good overview of the package is at Debian is https://tracker.debian.org/pkg/pyotherside
That package was removed from Debian testing, and a release critical bug blocks the package from re-entering Debian testing: https://bugs.debian.org/880093
That bug needs to be solved for pyotherside to get included in Debian testing, and from there automatically entering PureOS.
If you are familiar with Pyotherside then your help engaging directly at that Debian bugreport is much appreciated.
OK, looks like its not maintained anymore (from the issue comments at Debian site). I'll try to bump it as well, thanks for finding the issue. I am not familiar with Debian and wasn't aware of this check.