I’m talking about GNU here.
I just can’t seem to figure out on how to use either of them to communicate. IRCs don’t save older messages, but instead logs them. And I guess for the same reason, it is impossible to discuss anything in depth.
Mailing list is really hard to read, as it is nowhere similar to forum or tree-style comments. I can’t figure out what mailing list to message to.
For IRC you either need to setup your own client with bouncer functionality (meaning you need a server or a PC that is connected 24/7) or use one of the few modern IRC networks that have this built in. Sadly the big popular networks do not, meaning they are basically unusable without a bouncer. There is also IRCcloud and Source Hut that offer a bouncer as a service to their paying customers, if you prefer that.
Edit: You can also use XMPP or Matrix bridges, but those are a bit hit or miss and especially Libera.chat is quite hostile to them.
Most people use ZNC as a bouncer: https://wiki.znc.in/ZNC