The popularity of InspIRCd mostly comes from its modularity and out-of-the-box modules [1]. If you're looking for an ircd to replace Slack in terms of feature-parity, InspIRCd would probably give you the best start.
I used ircu until a few years ago, but these days it has mostly rot (maintenance, git/release tarballs code not matching, ...), and InspIRCd is pretty great if you need the customization.
I used ircu until a few years ago, but these days it has mostly rot (maintenance, git/release tarballs code not matching, ...), and InspIRCd is pretty great if you need the customization.
[1] https://wiki.inspircd.org/2.0/Modules