Perfect example of Clients, and Relays being more synonymous/ centered around a topic is nostr:nprofile1qqsdhc9kh3052kj50kjtyezgg6403r6xv4pkqsfsmraxvf39c84darcpzdmhxue69uhhwmm59e6hg7r09ehkuef0hlfkr9 being built by nostr:nprofile1qqsgwucgya472r8fhta8uh3hfe8uha0fskdzryv0xjawl5qqw34h6dgpzemhxue69uhhyetvv9ujumt0wd68ytnsw43z7qgcwaehxw309aex2mrp0yhx6mmnw3shyepwdaexwtcpr9mhxue69uhhyetvv9ujumt0d4hhxarj9ecxjmnt9utrktrk.
It is a Monero client with Monero relays, so it's fair to assume a fair portion of the activity would be centric around Monero, and other similar topics.
This is only one example of what's possible.