Well the look onto the blacklist gives more insights as sagemath is based on jupyter, which relies on jupyter-notebook and this got a depend onto npm. Last one mentioned is an issue for security and freedom as nodejs got removed.
Besides that: Hedgewars can get a proposal for an upgrade, for example doing this with on own PKGBUILD in own thread.
Yes, Hyperbola got some packages missing. But this underlines the major problems coming up with pragmatic ways some projects had chosen in the past. Not to mention that NodeJS got deep into the Github-universe some time ago, which makes this even more to a problem! Hyperbola got strict principles regarding that and I think this is a good way to keep real software-freedom up and running. Either the way: It would be helpful to list the missing packages or trying out to find alternatives here in this thread. Getting NodeJS or Java back into the repositories is no further option from my point of view as not only the licensing is problematic and those languages and packages based on them have so many freedom flaws. Better to left them out!
In general: Of course you can make proposals for getting packages into the repositories. Using the issues or with access onto the git-repositories on LibreGit to help adding packages. So you should also tryout building own PKGBUILD-scripts. But there is the warning: Using the ones from "Arch Linux" is not always recommended as many, really many packages there have technical problems with weak hashsums - so need a rework - technical or semifree up to complete proprietary dependencies. When having a closer look onto the PKGBUILD you can use the link source files - demonstrated here with sagemath itself. The PKGBUILD is the one interesting first, but you also need everything else to build your own package in the end. So the command makepkg is here your absolute friend into this: Download all the files (either with git or manual, therefore keep an eye that you use the plaintext-download and not the HTML-version) and try it. Nevertheless sagemath won't function at all because of technical and semifree / proprietary problems.
Human being in favor with clear principles and so also for freedom in soft- and hardware!
Certainly anyone who has the power to make you believe absurdities has the power to make you commit injustices: For a life of every being full with peace and kindness, including diversity and freedom. Capitalism is destroying our minds, the planet itself and the universe in the end!