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USB-based external DAC's took over. They very good now a days. Head over to audiosciencereview.com to see lots of DAC reviews, technical info and discussions.
"... The tl;dr of this book is a set of strategies to get 1% “better” each day..."
So after 10 years you will be 1.01^3650 = 5929448572069177.9 times better than you are today.. Good luck.
Vinyl record is just a temporary fad. CDs will be the next thing. After all the only advantage vinyl records have over CD's is the bigger artwork on their covers. All the disadvantages: worse sound, scratches, getting worse for each play, storage, maintenance of the record and record player etc. will come back in mind.
People would still like to own their favorite music, however, both because you can't always rely on streaming having the right edition of your favorite records, but also because you can show off your collection as a cultural signifier in your home, - just like books.
Before I got the Topping E30 DAC, I was using the Apple USB-C headphone jack adaptor, which is a great and cheap little DAC. You can read the review with measurements on Audio Science Review.
If you want SPDIF output, you should consider the Topping D10s, also reviewed on ASR.
Volumio is great, but I am now using moOde audio player (http://moodeaudio.org/) which is similar, but has much better DSP, in the form of CamillaDSP (it actually works..), also I find the GUI more intuitive.
I also owe a lot to Sir Clive. At 13 years old in 1981, My friends father bought a ZX80 for him. Some days after, I was at his home and he explained, what he had figured out about it. The same evening at home, I wrote my first program on paper (a Russian roulette game, I think). I couldn't wait until the next day, when I came home to him again, to see if my program would work. After some work we got it working :-) and I was hooked. I began buying the magazines "Your Computer" and "Byte", and even though English was a foreign language, I managed to understand some of it. A few months later, on my birthday I got my own ZX81, and after that an Acorn Atom, and then an Acorn Electron, and then a PC clone, and then... Still working with programming, now in data science :-)
This brings back memories. I used xlispstat for my engineering thesis on pruning of neural networks in 1992. I enjoyed it very much. I still have Luke Tierney's book LISP-STAT. I also used Splus, the ancestor to R, which was also very good, but not open source.