I have almost 50 containers running on a £75 used mini pc from Ebay, chucked in the bottom of a cupboard. Anyone that tells you you need a giant server rack to self host is a gatekeeping moron
The best way I found to combat spam was to change my email address. Was it a pain? Yes. Was it worth it? Absolutely yes.
Suddenly I can just give my email address out to services I trust, and I set up a temporary alias for anything I don't (although I tend to avoid those these days anyway).
I'm using Voyager, it's open source and is the best client I've used (I've also tried Jerboa, Blorp and Interstellar).
Upvote tracking is a feature you have to enable in settings, it doesn't do it by default. Also make sure to regularly take backups if that's data you care about because it doesn't sync anywhere.
I disagree that Nix is a solution in search of a problem, in fact it solves arguably the two biggest problems in software deployment: dependency hell and reproducibility (i.e. the "It works on my machine" problem)
Every package gets access to the exact version of all the dependencies it needs (without needless replication like Flatpaks would have) and sharing a flake to another machine means you can replicate that exact setup and guarantee it will be exactly the same
Containers try to solve the same problems, and succeed to a somewhat decent extent, although with some overhead of course.
I'm not trying to criticize you or your setup at all, if Debian alone works for you, that's fine. The beauty of open source and self hosting is that we can use whatever tools we want, however we want. I do though think it's good practice to be aware of what alternatives are out there should our needs change, or should our tools change to no longer align with our needs.
Doing this is generally a bad idea, because audio exported from YouTube is pretty poor quality, and music videos often have bits of talking or silence that make sense in context of the video but aren't part of the actual song (designed to prevent exactly this). There was a cli tool I used last year that could download music from Spotify directly.
Make sure to set the --download-quality flag to very_high if you have premium to ensure it downloads in max quality
If you have long playlists (more than a few hundred songs), you should also use the --skip-previously-downloaded and --song-archive flags as per the docs to make sure you can start again from where you left off, as Spotify will start to rate-limit your connection and downloads will fail (if this happens, just kill the tool, wait a few minutes and start again)
Last time I checked it only runs well on M1 devices, with M2 being somewhat usable. M3 though M5 are a complete no-go unfortunately :(