I boot my old 2010 Mac Pro in Mojave, and run the 32-bit (and thus obsolete) program RipIt. I still wish the author had made the jump to 64 bit; it did one thing, and did it well.
As silly as it sounds, building a digital library sure nice, but what will be the actual player involved in the end?
A full-featured computer, a handheld device, a SBC, other?
There's no significant complication here. Based upon how you "build" it, it can be as simple as AppleTV to access and display any of it on TVs around the house and easily watch on any Mac, PC or iDevice too.
The post I offered in #4 is one of the easiest way to pile up all forms of media and then easily watch it through a single (Apple made) app- no other special hardware required. Others have injected other wants into their setups and those use other apps and/or server hardware to accommodate their wants. However, once their way is set up, it's pretty simple to access any of it too.
The historical way was to fetch the media to be enjoyed, stick it in some kind of hardware, press play. The modern way virtualizes the fetching and hardware insertions. Choose the desired media from UI lists and click to play it.
I boot my old 2010 Mac Pro in Mojave, and run the 32-bit (and thus obsolete) program RipIt. I still wish the author had made the jump to 64 bit; it did one thing, and did it well.