In search of a self-hosted messaging client for my Jellyfin users

Good morning /c/selfhosted!
I run a Jellyfin server, complete with Jellyseerr, Sonarr, Radarr, the works. This has been a fantastic learning experience, and I've learned so much about networking, docker-compose, and what terrible tragedies and lost work can occur when you do not RTFM.

Now that it is up and running and stable(ish), I have invited friends and family to the instance. It is securely attached to my domain, and currently I have about 12 users.

Now, I have run into an issue: I need a centralized way for them to get notifications on new content and their requests being fulfilled, and a centralized way for all of them to contact me. Right now, it's a messy combination of sms/email/discord/phone calls.

My thought: I would love a self-hosted messaging client!

I'm wondering if anyone knows of any messaging clients that meet the following criteria:

1. Grandma-level user friendliness, if possible
2. One-way multi-user broadcast option
3. Jellyseerr integration, or some back-assward way to get it to work with one of Jellyseerr's integrations
4. little user-to-user communication

Ultimately, my goal is the following: An app that I can use for users to submit questions and bug reports, and that I can use to broadcast news and updates, downtime notifications, and other messaging. Ideally, one that supports a "bcc" option. An additional caveat is that the users should not be able to easily find and message each other, I don't need my conservative coworkers meeting the queer ass polycule that makes up 20% of my users.