Nah, the base libraries such as glibc are usually the same, so most of the time, an application designed for GNU/Linux will run on any distribution.
It's more that the stuff like user interface and things like maintenance such as package managers are different.
There are some choices to be made for distributions though, such as are you running systemd or OpenRC? Which could be important, as some applications (e.g. snapd) require systemd and won't run on systems using OpenRC.
This is correct. As you've been told several times now, Linux as such is not an OS at all--it's only the kernel of the OS. To have a general all-purpose OS, you must (as Osiris said) add a number of other applications and libraries. These together comprise a Linux distribution or distro, and different distros have different ways of doing things--which is why there isn't a general set of instructions for "Linux." All of which you've been told repeatedly, in this very thread.
I appreciate not only your generous donation, but your kind words and encouragement. If you wish to write up your thoughts, you can click on my username above any of my posts where you should find a "Message" button that will allow you to send me a private message. I'm really busy with my dayjob lately, but when I next find time to advance CertSage, I can take a deeper look into what you've written.
I do think the most relevant thing here is the list of prerequisites on the Certbot page ("to use certbot, you'll need" section). Several of these prerequisites are not really met for GoDaddy shared hosting.
This is more closely related than you might think to the "GoDaddy not telling you which Linux distribution you are using" issue, because the main reason that the Certbot page asks these questions is to figure out how to administratively install custom software on the web server. (Which is different for different Linux distributions.) However, GoDaddy does not permit you to administratively install custom software on the web server, so it's not that surprising that they also don't tell you information that would be especially relevant to figuring out how to do it (because they don't all it).
If you happen to want to answer the underlying question even though you probably can't usefully use Certbot in that particular environment, you could try running
lsb_release -a
at the command prompt on that server, and you're relatively likely to get a correct answer.
I was at EFF when people spent quite a bit of effort trying to figure out how to balance the "how do I use Certbot in different situations (when I already know that it is relevant to me)?" vs. "is Certbot relevant to me at all?" issues. Increasing the amount of emphasis placed on one question might potentially annoy people who are most concerned with the other question. But if anyone has an idea about how to make the "Certbot may or may not be relevant to you" aspect clearer or more helpful, I know the EFF web team would be interested in trying to improve that!
By the way, when I started using Linux, it took me about two years to clearly understand that there were different things that different people meant by "what version of Linux you are using". (There's the Linux kernel version, which you can find out with uname -a, and there's the distributor release version, which at that time there was no standard way to find out but which you can now find out with lsb_release -a.)
So I definitely understand how non-obvious the ambiguity about the meaning of "version of Linux" can be!
The variety of different systems based on the Linux kernel sometimes pleases people who strongly prefer one or another, but sometimes also annoys third-party software developers (who have to try to support a very wide range of operating systems based on Linux) and tech support providers (same...) and hardware manufacturers (same, assuming that they care enough to test the different operating systems with their hardware).
If you wish to write up your thoughts, you can click on my username above any of my posts where you should find a "Message" button that will allow you to send me a private message. I'm really busy with my dayjob lately, but when I next find time to advance CertSage, I can take a deeper look into what you've written.