As a for-profit, they need to make a profit. Recent layoffs show they're likely struggling, or at least not doing great. Unless they can find a way to monetize photos, don't expect an app.
CrashingMonkies
I self-hosted Wallabag for a while. It's nothing fancy but has most of the basic functionality you would expect.
The primary use case of Plex is to allow you to view and listen to your own media files: movies, tv shows, music. If you have a lot of those types of media files, then Plex is very useful. It can do a few other things, like let you view your photos and watch some free movies/tv offered through Plex the company, but I don't think the majority of those who run Plex really care about those.
The short version is that you install Plex, point it at your media files, let it index those files and download all the metadata (cover pictures, actors, etc.), and then watch. Plex has apps for most media players these days, including Chromecast. You would install the Plex app on your Chromecast, log into your Plex account/server from the app, and then you'll be able to browse and consume your own media files. You do need to buy a Plex Pass to consume your content from a mobile device.
To use it from your office, as long as your company isn't blocking it on the network, then you would just log in through the browser and consume your media files that way. One thing to recommend Plex over Jellyfin or Emby for the relative newbie is that Plex handles the authentication and relaying of traffic between your server, so if you're not comfortable setting up a reverse proxy or VPN to access things on your server from the outside world, Plex handles that for you.
If you have any more questions I'll do my best to provide helpful answers.
I've had a jmp.chat number for 2 years. I have most of my accounts, credit card and banks tied to it. Been very happy with it. It is like any virtual number in that there are some services that won't accept it.
I use syncthing to upload my Android phone photos to my Unraid server and then use Photoprism to manage them. I use Duplicacy to backup photos (and other data) to Backblaze. I tried Immich briefly and just preferred the setup and look/feel of Photoprism. To be fair, that was about a year and a half ago, and I know both apps have grown a lot since then.
Another +1 for Plexamp. It's enjoyable and easy to use and they're very actively developing and supporting it.
TL's been working fine for me, except for the little bit they were offline last week. I had to point my download client to torrentleech.cc because they had to enable Cloudflare on the .org domain.
For me, it's a replacement for Feedly. I use a browser to access it on desktop and FocusReader on mobile. I like to own my data as much as possible.