~Tl;dr~
If your app is accepted / added by Snap, i.e. you can type:
sudo snap install --options myappname
...in order to install your app, it will be in the "Snap store/Software Center". They are one and the same.
~Detail~
To add an application to the software center(s) it needs to be a .deb package, first of all. In order for it to be properly installed into Ubuntu OS it must be a Debian package. I believe this is done in a few steps, the first of which involves autotools.
The standard is overseen by GNU. This guide will tell you everything that you need to know.
As for getting your .deb package to the "Software Center", the key is first knowing that, for the last few versions of Ubuntu, the "Software Center" is just a front for the snap store. Every app you download there comes as a snap.
So the info for which you need to be searching is "how to get my app as a snap." Here is a great resource on the subject.
As for the language that you need to write it with, it doesn't really matter, at least in this context. Most have traditionally written in C, but one could probably find a package out there containing any combo under the sun.
Sure, the package will need to be runnable in the target environment, but a package is a sort of container, so you can just include your own environment inside it.
If you build with Python, why not just build to a virtual environment and pack the whole darned thing? That way it runs on the same interpreter each time. Same with Java and the JVM, C/C++ and the GCC, etc.
You also include any dependencies that your app needs. This includes not only runtime dependencies, but installers etc. as well. These are usually just Bash scripts, but again, language doesn't matter.
Honestly, what is inside the package is standardized (you will need a certain type of open-source license, etc.), but all the debian system is concerned with is the interface. Dpkg needs to know what is going on at install time. As long it is given clear understandable instructions so it knows where to put everything, and the result is a system of apps that behave as the user expects, you have a valid .deb package.
That said, if you want a valid Snap package, I can guarantee that your restrictions will be a bit tighter. Best to follow the standards I linked from the get-go.
EDIT
I just recently found a couple resources on Github which automate the build and publish processes for snaps. They are both github actions maintained by Snapcraft. With the combination of these, any compatible application can be turned into a published snap.
They are located here (snap builder) and here (snap publisher).
