I’m working on a project that needs a similar approach to slack or discord. I know about matrix, but the person I’m working with said to be open to use a fediverse alternate when I tell them I didn’t want to use slack. I mention matrix and the fediverse as an alternative and they asked me a good fediverse option.
It’s needs to be good for team collaboration, easy to set and be able to maintain original images quality.
They’re from a good while before, and I’m not sure it would be appropriate for your use case.
Matrix is much closer to the Slack / Discord format. It IS a bit more complicated than those two, especially if you’re self hosting it, but it has a lot of similar functionality