Probably C++, Zig, and possibly Clojure (the latter two maybe after solving it in C++ to compare how I might approach the problems differently in them). Not going for speed in coming up with solutions, mainly will try out various libraries I might not have touched before or rarely used, and brush up on newer C++ standard features.
I don't use Calibre for this (but I do for epub and pdf ebooks). I use Plex and use Plexamp for my music collection. For audio books I used to have Chronicle Audiobook Player installed (which is open source, but not actively maintained) but am now trying out Listen Audiobook Player (which is not open source as a heads up). Both of those allow me to download books wherever I am.
If you have no interest in running a Plex server neither of them are suitable for you, but I just wanted to mention this solution in case you're not dead set on using Calibre. Plex has a cost factor which may come into play (an obvious non starter for some). I have had Plex Pass for a long time so it was natural for me to use it, but might not be for you.
I have used several, the first I used was RedSquirrel which later evolved into the commercial Virtual Acorn. After RedSquirrel stopped getting updates, have mainly used RPCEmu.
I loved RISC OS. I got the computer in '87 or' 88, while at university. Such smooth multitasking for its time. For school work that involved writing some programs, I fired up the PC emulator in order to run Turbo Pascal. It was sweet seeing a virtual PC running in a window while doing other things in other windows. Writing graphics programs with GUIs (Acorn C) instead of just creating image files like most of the other students did was fun too.
I loved my A310 at the time. I'm not so much of a hardware person though, and I'm not sure I can get it working in the US, despite the rush of nostalgia it would mean. Main issue would be getting a monitor going with it.
The Shannara series by Terry Brooks, with the shortlived Shannara Chronicles TV series (it was not specified the show or movie had to be good...)
A Fedora Linux container on Proxmox. I have no stability issues really.
According to a news article about US MIL emails being accidentally sent to ML addresses due to misspellings, there was apparently a contractor in charge of the ML TLD, whose 10(?)-year contract was up the other day, I think, or will be soon. With Mali taking direct control over it, presumably they have their own ideas how to manage it. Why they wouldn't or couldn't have had the contractor do it (charge for domains) a long time ago, I have no idea. Doesn't seem like something that would have to be postponed until the contract was over, but obviously I have no insight into the details of the matter.
Since I can't see any other reference to it, I want to mention I'm using openmediavault and export smb mounts for my windows computers and NFS for Linux. It is running in a VM in proxmox. Works well enough for me. It is my in house backup destination, and my Plex media files storage (plex is running in a container on the same proxmox host).
Like most and probably every other mentioned solution, accessing the nas/shared storage is not more difficult than just opening windows explorer on windows and selecting the network location, etc. I'm sure it is easy on Mac as well, but I don't use apple products myself.
Plexamp is my primary music playback in the car commute if I'm not listening to an audio book. Love it.
Maybe you will find Blood, Sweat and Pixels by Jason Schreier of interest. Been a little while but I enjoyed it as an audio book.
Real kidnappers will not be happy about this as deepfake becomes more prevalent and calls for ransom gets ignored more and more. Do they have union that can go on strike to raise awareness about this?
Proxmox with a bunch of small dedicated lxc containers (running small Ubuntu lxcs mostly). It works for me anyway, though I don't use any of the rr programs. My Plex lxc gets its Media files from an openmediavault NFS mount (Running in a VM instead of lxc), and I use smb file sharing for my windows desktop to access the same files. Your mileage may vary, what works for me night not be for someone else.
One of them could be born February 29 and lose out on a bunch of birthdays compared to their twin.