kuroSlack needs payment to have group calls. Also it would be nice to move something open and ideally something self-hosted.
y0kai [he/him]matrix maybe?
ZootMatrix is no where near the level of discord, if all you need is a chat app than ya sure, simplex or Matrix work great. If you want feature parity… Definitely not either of those two, as they are just glorified sms/group text apps.
Plus there’s the fact that Matrix is heavily user unfriendly