This will be an unpopular suggestion here but why not just go all in on iCloud? It’s reasonably inexpensive for not data-hoarding amounts of data, reasonably secure and E2E encrypted. Given the low cost, zero setup if they’re already Apple people and lack of admin I think it is ideal for them.

I pay for iCloud storage because I want HomeKit Secure Video cloud storage (I also have a local copy on disk).

As a long time plex pass user, is there anything there that would make me want to switch? Plex has just plain worked for me for years. mobile apps, everything is just great. Why should I look around?