Snap will never replace the package system which is like a backbone for a Linux distribution. This is just another way to install an application, a special kind of package with a bunch of dependencies that might not be the same than the ones that are installed in the system.
Now if you want for example the new version 2.4 of Polyphone that I'll upload soon, here are globally the steps in the Linux Eco-system before a user can install it with APT:
- as the owner of the GitHub repository for the Polyphone sources, I will flag a specific state of the sources with a tag 2.4
- then alerts can be emitted (if watchdogs are set) to different packagers that will build and review this version, each packager with it's own Linux distribution
- I might be contacted to fix license or compatibility issues and when everything is OK, the package will be part of the unstable Linux distribution of for example Debian or Fedora (each distribution has it's own rules)
- after some time (when a stable state is considered), it will be part of the stable version of the distribution.
The whole process might be long, that's why I build myself some packages and upload them on this website but I cannot unfortunately build Polyphone for all versions of all distributions.
The last option, I think in your case if you want to quickly have the latest version, is to build the software directly from the sources, as explained
here.