I know Teams doesn't live on the intranet, but I'm not going to put work software on my own phone. Policy needs it to set up a work profile and I then can't use fingerprint, face or a 4 digit pin. And all the shite that flows through Teams would be be piling up, just like it does on the PC at work, brilliant when you're only in a couple of days a week. They want me to use a phone? Provide one.
The WhatsApp group is for us to send updates about traffic, if someone can cover a shift etc. it's not an official work thing. I could of course not use it and just text people. That's really just making my life difficult whilst sat up here on my high horse with a self righteous look on my face, whilst I miss the chance of an extra shift.
Denying putting work stuff on your phone is absolutely valid. The company should provide a company device in that case. And if you do agree to put company data on your phone, they should give a monthly stipend towards your phone bill. That's how every org I've worked at has approached it.
Really depends a lot on the groupchat. I was apprehensive but it's quiet there and overall the things that get sent there are either in office hours (e.g. "internet might be out intermittently we are working on a fix") to links to pay for something someone paid for outside of work like food or drinks.
I don't mind it that way, maybe once a week a couple messages
…to which for privacy reasons your team shouldn’t like SMS, Discord, Telegram, Slack, and probably even Signal (somewhat for privacy, & more for accessibility)
XMPP. A business can self-host, there are public servers, or there are many businesses which offer customised xmpp hosting as a service.
I can be federated with other xmpp servers or be a locked-down work-only service, or federate with chosen other servers (such as a client company's xmpp servers).
If that's the main problem then that's easy to solve! Simply use a free public xmpp server.
I mention the self- and paid-hosting options because businesses tend to like having a sevice agreement backed by a contract, and may have additional specialised requirements not provided by free services (xmpp or otherwise).
Snikket exists for this type of user. If money is an issue, since XMPP is actually lightweight unlike Matrix, you can host multiple things even on the cheapest VPSs so it isn’t dedicated to one taskl or self-host out of your home (which is what I do, but also with some small sites, a feed aggregator, Mumble, terminal sharing, Darcs/Pijul version control systems, & Nix remote builder).