Same story here. Between Netflix and Hulu everything I wanted to watch was available for like $25 a month. Then all the other streaming services started coming out, less and less of what I wanted was available. 40TBs later I'm not subscribed to a single service and everything I want is back in one place. The arr stack made everything so easy. Fool me once shame on you, fool me twice, well, can't get fooled again
I took a Lenovo M9 and stripped it everything I could added my favorite eReader and audiobook apps and use it exclusively as an ebook. It was under $100 and the only thing I wish it had was an e-ink screen otherwise the size is perfect and it works wonderfully.
When I started my media server in 2020 I used e-waste from my building. Had an i7 3770, 16gb ddr3 ram and an rx460 graphics card. I ran jellyfin, ultrasonic and audiobookshelf for 10-15 people with no problem on this hardware. Anything made within the last decade should provide a good starting point for you.