Same. I used mIRC back in the 90's, but ever since I started dabbling with servers I preferred to have an irssi client running inside a screen session somewhere. Allowed me to catch up on things that happened while I was AFK, as well as provide some continuity while I was on the move and/or on a dodgy connection.
Unfortunately it's practically unusable for my use case, which is talking in CJK channels on non-UTF8 servers (when the channel name also has such characters), because recode support has been broken for 20 years.
You know, I wish I could enjoy IRC - or chatrooms in general. But I just struggle with them. Forums and their ilk, I get. I check in on them and see what's been posted since I last visited, and reply to anything that motivates me to do so. Perhaps I'll even throw a post up myself once in a while.
But with IRC, Matrix, Discord, etc, I just feel like I only ever enter in the middle of an existing conversation. It's fine on very small rooms where it's almost analagous to a forum because there's little enough conversation going on that it remains mostly asynchronous. But larger chatrooms are just a wall of flowing conversation that I struggle to keep up with, or find an entry point.
Anyway - to answer the actual question, I use something called "The Lounge" which I host on my VPS. I like it because it remains online even when I am not, so I can atleast view some of the history of any conversation I do stumble across when I go on IRC. I typically just use the web client that comes with it.
Weechat. Terminal based, flexible scripting system using a handful of languages, still actively developed, and I can make it work the way I want it to work.
Already coming up close to 10 years of The Lounge! Really gets the job done nicely as long as you don't hate webapps. By far the least broken option for mobile unless you go IRCCloud.
IRC's not as popular as in its heyday, and while once it was the main choice for multi-playing gaming chat (Quakenet et al), that's largely gone elsewhere, but it's still very good for certain technical channels.
IRC has also proved to be remarkably resistent to commercialisation, mostly due to the users. Even when one of the biggest networks, Freenode, got taken over by a drug addled mentalist Reference who started insisting all all kinds of strange things, the users just upped sticks and created a new network. A bit of fuss, but the important stuff stayed the same and it's continued much as before as a new network, Librenet.
Discord is closed source and has no way to easily archive/record conversations. This makes it unsuitable for a lot of open source projects who need a chat client. I've not used much Discord but potentially the "gamer" culture might put people off.
Matrix seems good but it's not quite there yet from what I can tell. It's got way more features than IRC but none of them seem to work that well. Like a swiss army knife full of blunt tools.
For IRC I'm on the libera.chat server. Usually hanging out in the gentoo channels since I use that distro. There are a lot of different channels for the various devs, user tech support, niche uses like gaming* and also offtopic chat channels.
*More gamers tend to use other linux distros for some reason
srain, becuase of being modern gtk, because of being light on dependencies, because of being available on aur, and because I'd like it more (yes there are several things that are also a matter of taste) than the alternatives, :)
Convos - self hosted web based client written in Perl of all things, because it's small, simple, does exactly what I want and no more, and avoids my having to faff with client + bouncer which was getting old 10 years ago and feels positively withering now.
WeeChat! I've been using WeeChat for like 13 years now and I love it. I used to use irssi back in the days and mIRC before irssi existed.. Some bitchX experiments may have happened at some point during the shell boom too.
This remote interface is the biggest selling point to me even today, it's amazing: WeeChat-Android.
Haven't tried halloy, but it sounds cool, I wish rust build with shared libs in mind, instead of everything link statically, but it sounds interesting, I'll see how it is compared to srain which is my current choice...