It gets a bit more complex if you want to run your own server, but that's not something you can do at all with Slack.
For a small corporate team that wants to pilot a chat program, like in the original comment, the gulf between Slack setting up your own private workspace with a few clicks and a room that has all of your chat history exposed to any user that knows the room name is pretty large.
I would love to see riot or matrix give you a few click options to have them host your own private matrix server, as that's a big obstacle for corporate customers who don't have the resources (human) to spin up their own servers (domains, adding ssl certs, adding nginx, etc.) just for trialing a chat program.
Separately: we're working on providing a "one-click" homeserver hosting option with a free trial precisely of the kind you're asking for.
TheLounge - https://thelounge.chat (FOSS, self-hosted)
IRCCloud - https://irccloud.com (mobile clients OS, hosted)
At the very least it looks and feels far more modern than, for instance, mIRC.
I'll stick with Slack.
One problem with all these closed client apps slack (with this update)/whatsapp/telegram is that there is no way to verify/audit it is actually doing proper e2e.
Users must trust the X company that they are really doing proper e2e.
These apps should allow users to download a plugin and use that to produce the e2e. Then the user would be able to download an open sourced audited plugin that encrypts the messages before they hit the whatsapp/slack/telegram company servers.
So for instance, if this was possible, everyone on a group would download and install the plugin that runs on top of whatsapp/slack/telegram and share an encryption key that only they know about. And do the same for conversations between 2 people.
There must be some point of trust, however with the current situation, it is hard to trust e2e code no one is able to audit.
Or just open the protocol so everyone can use and create their own clients and their own e2e mechanisms. Which is what IRC is.
The freedom to choose is one of the reasons people wish slack would open source their protocol.
I've never used Slack but these name drops are all familiar.
Back in the good 'oldays of Eggdrop? It's amazing that Slack was "backwards" compatible with IRC for so long.
But honestly, their API is mature. No need to be backwards compatible. Easier to sell when you are in control of access and client.
(Arghh... I'll probably be downvoted to hell for a flippant, drive-by comment, but what the fuck... We all know that HN hates comedy.)
Some people like slack or telegram because they provide an API for BOTs. Something IRC has been open to since the begining.
Non power users might have trouble using IRC with the usual clients (mIRC/irssi/bitchx).
Today a family member, not technical and 60+yrs asked about "that tool" that is like whatsapp however it allows users that just joined a group to read old messages. He was referring to slack. He wanted to create a group and when new users from his company joined, they would be able to read whatever was written on that group.
So with this in mind, i think what would really work (also) is to have something on the front of IRC (some bouncer) with a pretty UI that logs everything and allows new users to connect via mobile, standard irc clients, and also send pictures, and read backlog (stuff slack does). However the backend chat server should be the decentralized existing ones, efnet/freenode/etc.
So maybe its time to re-invent slack and make a pretty UI to access usual standard IRC. ie. a new slack that uses old irc networks (decentralized networks) as its backend. But also allows users to talk from mobile apps, browsers, etc