(Disclaimer: yes, I bought a $180 4TB Crucial SSD too, but my family split the cost with me since they're going to use my Jellyfin server. Whether that counts towards the final cost is up to you. And the electricity cost is pretty negligible to run a Le Potato as a server, but I guess you can count that too.)
So this all started rather innocently. I was fed up with all the ads being shoved in my face with everything I do, so I finally decided that it was time to set up a Pi-hole on a single board computer. For me, it ended up being a Le Potato. I had never even touched Linux prior to this, so it took me a day or so to get everything set up. I love learning new things so I kind of got hooked on learning my way around Linux basics and decided that I was going to upgrade my setup to a Pi-hole + VPN using wireguard. That was kind of a beast to configure as a novice but I got that to work after about a week. Now I was getting ad free content anywhere I wanted on my phone. I rode that high for a few weeks until I realized that I was just scratching the surface of what I could do with my little $30 Linux server setup and this is where I really got to upgrade.
I had learned of Jellyfin from LTT and decided that I was going to test it out. I set up the Jellyfin server on the Le Potato and I was off to the races. Now I just needed content. I read through some of the wiki and settled on Mullvad+qbittorrent to find the content I wanted. With everything configured it still didn't really feel complete, so I set up profiles for my family members and gave them their own passwords to access the content. I quickly realized that 64 GB was not nearly enough (without a rolling library) and I was getting annoyed with having to constantly swith the flash drive I was using between the Le Potato and the laptop where I was downloading my content. So I went out and bought a 4TB USB SSD from Crucial and set up access as a NAS on Ubuntu with Samba.
It's just now finally set up. My family texts me to let me know what it is they're wanting to watch, I torrent it, upload it to my NAS, and Jellyfin streams that content to my family 100% free. I've turned my 6 family members into pirates and they barely even realize it.
... or you could pay approx $2.70 / month for real Debrid. Replace jellyfin with stremio + torrentio and your family can immediately stream whatever shows they want w/o asking you and without needing to wait for the torrent to download.
This would be my preferred option, but: I do applaud OP's enthusiasm and dedication. He's learnt a lot of things about it, whereas because of my setup (as you described) I know fuck all. Plus, having his sort of setup gives you your own library over time (should that be desired).
Yeah, it was a fun hobby over the course of the last couple months and I learned a ton about linux, networking, server infrastructure (kinda), and troubleshooting!
I don't like to be reliant on someone else's software or hardware either, so that played a part as well. The library part is good as well because my family is much more likely to give a TV show or movie a try if they see that I added it and we can talk about it when I visit.