yes, they are. reread the post, I just did so and I'm still confident

sorry, but I think what you are looking for is platforms like Lemmy. it is not centralized, it is distributed. not peer to peer, sure, but

• since a lot of devices are not being online at the same time, mobile phones but even desktop PCs always go offline for some period of time, the direct communication wouldn't really work with a lot of other users
• you would need to store much more dataon each of your devices, unless you're the kind who doesn't care about mindlessly deleting past conversations

No, not really.

The problem is that OP is asking for something to automatically make decisions for him. Computers don't make decisions, they follow instructions.

The computer is not asked to make decisions like "pick the best image". The computer is asked to optimize, like with lossless compression.

did they also move the HS to the phone?

I only have Telegram and Matrix. SMS? To me that sounds to be a huge step back, even from Telegram

I don't see it, probably it was removed again

oh there is. from 3 years ago, and some

This is something I want to know too!
I don't believe google deletes anything that has entered their system, my use case is that they don't have visibility on when are my devices online, how many so I have, and such. But my gmail address has not been my primary one for long, so it's not that important.

All I have found so far, though, is that what I need is possibly called a Message Delivery Agent.

They could still be compatible, though. it's possible even today, to some degree

At least in the case of jellyfin, it's not exactly just a "resource hogging frontend".
For instance it keeps track of watch progress, in episode and through the series, and what did you watch last time so you can continue with whichever.
Allows you to remote control your player device (handy if it's a TV or something like that) from your phone or another anything with a web browser.
It fetches info about the movies and series so it looks nice and for your users it is easier to pick something for themselves.
It has integration for MPV (and probably a few other players) so it does all the above.

And it does all these things in a way that everything is available across all your devices. Not just the content, but watch progress and everything else.

Something tells me you also tell your family that a Linux computer with no desktop environment is all one needs for everyday tasks.

And finally for OP: you don't have to learn FreeBSD for ZFS, because Linux has it too. Because of licensing issues installation is a bit more complicated in most distros, but if you use Proxmox, they have done that part for you.

I'm pretty sure that on Linux I did not need to disable all functionality to upgrade

Any time on Linux, but the windows shells are unusable. And configuration databases are much more convoluted things on windows than text files