Slack has made using their API much trickier over time: getting a token to post these days (officially) is under the control of the server admin (as one needs to add a "slack app" to get one). One can extract a token and some cookies from a web browser slack session still, but it's not as clean as it used to be (where one could just generate account associated tokens that didn't randomly expire).
In other words:
- to use the slack APIs, you probably need company level buy in _before_ any code is written against the API from IT folks
- in contrast, with IRC one could just try something out and at some point in the future _maybe_ create a seperate IRC account for it, if your IRC server even has logins enabled. If it doesn't, which when I worked for IBM was the case, one can just pick a new username for the IRC bot.
I think the op meant on the protocol level, not client. You can literally do `cat mycommands.txt > /dev/tcp/...`. IRC is pretty simple, I remember using telnet just for fun to connect (also the PING message replies are annoying to type yourself) and at one time, (ab)used an FXPable FTP server data port trickery in ASCII mode to send a message to a channel.
Due to its simplicity I could see its application as a falback for global communication downtime/outages (as we had with FB/Insta recently).
https://github.com/csabapalfi/slackcat