network noob here with 0 knowledge. what i know is fopnu has indexing server indexing how many and which channel. why darkmx instead needs to select which network to join then channel?

Another noob and darkmx novice here. Maybe because networks work as a hubs and their sole purpose is to two-directionally gather (eg. sync) and connect file shares and channels according to advertise bit and group name settings?

to add to previous reply ...not only file shares and channels but also other networks. That allows making either separate islands of networks or connect those.