Mattermost

Wir nutzen die freie Version. Besonders wichtig ist uns Mattermost als sichere Kommunikationsplattform in House

Einige Funktionen, wie chatexport sind in der freien Version nicht nutzbar. Die kostenpflichtige Variante ist aber preislich nicht attraktiv für uns

The interface is pretty much self-explanatory. This is why the user acceptance is quite good. Customizing the interface is straight forward and can be done at user level.
The open source cummunity around Mattermost is really nice and welcoming.
Apps for every operating systems are available and easy to use once manually set up.
Scalability was never a problem with 1000+ users.

Setting up integrations is more complex than with Slack, where integrations can be installed with one click in the backend. There is an app directory, but the apps need to be set up manually. Once set up, they just work. Incoming webhooks are the only exception; they work out of the box.
Mobile perfomance is gradually getting better, but it's not yet up to Slack's par.
The Windows-app is not yet ready for big scale rollouts via group policies.

Mattermost is constantly being developed and you can tell that it's going further. In addition, as a collaboration tool, it provides the most important information. No more and no less.

At the beginning (approx. 2018) it was still a bit unstable and some important features were still missing. This has gotten much better in 2022. Over the years, with many users, maintenance and upkeep should never be neglected. Otherwise it will be slow and have long loading times when changing channels etc.
Plugins work, but not all are mature (e.g. Jitsi caused problems for us)

Slack integrations just work on Mattermost. The theme choices are very nice. The ability to host my own on-premises server is very nice. Technical support staff is very knowledgeable and competent. I'm not made to feel like an idiot if there is some specialized knowledge that I don't have.

The Android client is extremely buggy and fairly slow still. Selecting a push notice to open Mattermost to view and respond in the thread does not always open the right thread and is always slow (even on LAN, with the latest gen of Android phone!)). The client MUST be snappy and it just.. isn't.

The Windows client becomes slower and slower the longer you have it open, so it must be restarted every day or two. It's a little buggy; sometimes new messages make your view scroll up instead of down. But it works well enough most of the time.

We switched to this product because of lower price and option to have self-hosted messenger. Allows you to create secured and perfect internal communication and collaboration tool. Video calling and file sharing is also implemented. You can prioritize chats making them favorite. App runs smoothly.

Sometimes we have problems with video calling tool. Also sharing images in some formats make us some troubles.