I don't know the answer (I don't care about numlock myself), but the arch wiki has an article on this: https://wiki.archlinux.org/title/Activating_numlock_on_bootup
Perhaps that will be useful to you. In general checking the arch wiki is a good idea for any Linux issues, even if you don't run arch, many things still apply to other distros and the articles are of very high quality.
In this case, "Early bootup (mkinitcpio)" would likely not apply to most other distros that aren't based on Arch, but the rest looks to apply widly.
It is worth noting that in the KDE section it mentions the need to apply two settings, perhaps that could be it?
Agreed, I run arch on my desktop and laptop, because it is more stable (in the sense of fewer bugs, things like suspend/resume works reliably for example) than any other distro I have used.
But on my VPS and my Pi I run Debian because it is more stable (in the sense of fewer upgrades that could break things). I can enable unattended upgrades there, which I would never do on my Arch system (though it is incredibly rare for those to break).
Also: if someone said they were a (self proclaimed) "semi noob" I would not recommend Arch. I have used Linux since 2002, and as my main OS since 2006. (Furthermore I'm a software developer in C/C++/Rust.) While Arch is a great distro, don't start with Arch.