Bulletin board system
While bulletin board systems (BBSs) are mostly historical, there are still some alive today and some are still on FidoNet and other similar networks. Like the SmolNet, they are hard to archive, because they are usually accessed using dial-up, telnet, rlogin, ssh, SmolNet or other protocols, which aren't representable with the WARC format. Some BBSs do have web or FTP gateways, but often they are just gateways to the telnet interface, rather than websites with URLs that can be archived. BBSs may have associated Forums.
A list of bulletin boards with web access:
https://www.darkrealms.ca/ job:a8r12a5j6euqx6sq0yy9yk1qk
https://www.ipingthereforeiam.com/bbs/ job:2exrhf342dr832ll92uolcptr
A list of lists of bulletin boards:
http://www.synchro.net/sbbslist.html
A list of bulletin board software: