As a related aside, the terms "cepstrum" and the "quefrencies" [1] (c.f. spectrum and frequencies) sound so hilarious that when I first heard about them I was convinced it was some kind of prank.
Mathematically, the Fourier transform is "simply" a way of representing time signals in a certain orthogonal vectorial basis. Vectors in an ordinary sense, e.g. a displacement vector on Earth's surface can also be represented in several orthogonal bases: one basis could, for example, be two vectors pointing North and East; another could be a vector pointing along a certain road and one perpendicular to it. There is nothing inherently special about any of these bases, one could draw maps according to any of these two or many other conventions. (Orthogonal basis vectors are not even necessary, only convenient.)
The interesting thing about time-dependent signals (or any "pretty" function, really) is that they live in an infinite-dimensional vector space, which is hard to imagine; but (besides some important technicalities) the math works mostly the same way: signals as infinite-dimensional vectors can be represented in a lot of bases. One representation is the Fourier transform, where the basis vectors are harmonic functions. The "map" showing the shape of a signal as a combination of infinitely many harmonic functions -- i.e. the frequency domain -- is just as real as any other map with different basis vectors, e.g. the Walsh–Hadamard transform mentioned in the article. And, crucially, the original time-domain representation is also just one map showing us the signal, though it is often the most natural to us.
1. Yes, I think all HackerDaily articles should be included. 30-50 articles per day is not that much.
2. I think separate RSS feeds for different timezones might be better (not _every_ timezone, but say, every whole hour offset), so everyone can choose what they want; either based on the timezone or on their daily routine.
I have been using /e/OS on a Fairphone 3 for several months now, and I am quite satisfied.
Yes, it is built on LineageOS, though I am not sure how closely it is tracked.
They have their own cloud services, but you can opt out. You can use your own Nextcloud server as well, which I think is pretty neat: you can have a convenient cloud-based experience (contact and calendar sync etc.) with the stock /e/OS installation, while also having ownership of your data in your Nextcloud instance. (Their own servers are also heavily based on Nextcloud.)
Regarding app stores: I think it is the weakest point. F-Droid is nice but not enough, the /e/OS App Store is a bit murky for me; for most of the non-FOSS apps I use the Aurora Store, which seems trustworthy to me so far.