I'm sure this gets asked a lot, but what ecosystem would be most favorable for my use-case?
Here's what I want... I want a central storage location for all of my extended family's family photos and videos. I want it easy to access and share from computers, phones, and smart TVs. I would also like each family (siblings' families) to be able to have a private folder for cloud storage.
I know that I can purchase a Synology NAS and take advantage of all of Synology's apps for phones, computers, smart TVs, etc and this would suit my needs perfectly.
However, I know I could also build a custom machine with TrueNAS, OpenMediaVault, or the like and use Plex, Jellyfin, or Emby for streaming the family videos and pics, and use something like NextCloud for access to personal storage from mobile, etc.
For my use-case, is there any reason why one ecosystem would be better than the other?
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.