We do something similar to Zulip that is (in my opinion) a little easier to use, Aether (https://aether.app). Its also thread based, but it’s a little more in the line of Slack and Discord in terms of design. So far as we can see it’s been a fairly easy uptake moving from there.

Also helps that we have a full email coupling, so if someone in your team doesn’t like or want to use the app, everything will stream to them just as regular email threads they can respond. This is useful for older folks who prefer email, or higher up people who don’t want to deal with an app but still be able to follow what’s happening.

Here’s a comparison of how that works in one image: https://i.imgur.com/wLFnIyn.png

If you’d like to try it I can throw in a discount code, just reach out - my email is in my profile.