We are digital librarians. Among us are represented the various reasons to keep data -- legal requirements, competitive requirements, uncertainty of permanence of cloud services, distaste for transmitting your data externally (e.g. government or corporate espionage), cultural and familial archivists, internet collapse preppers, and people who do it themselves so they're sure it's done right. Everyone has their reasons for curating the data they have decided to keep (either forever or For A Damn Long Time (tm) ). Along the way we have sought out like-minded individuals to exchange strategies, war stories, and cautionary tales of failures.
I think you'll probably be installing something like plex on a custom built or a synology.
It's more of a question of how much time you have and budget. Do you want something with nextcloud like functionality out of the box? Synology isn't a bad choice. It has all the apps for cloud backups, quotas, users, etc.
Do you want to toy with your system more? Roll your own and choose the best software for your needs.