I opened a ticket with Raptor, who reached out last night and indicated that my problems mirror an issue encountered with more new Blackbirds than my own. Quote:
“Quick question -- have you been able to access the network from the installed OS or is that also broken? We're tracking down a potential issue with the new Blackbird programming line, hence the question -- the symptoms match an older issue we had seen and thought was fixed for the production line.”
Also, I swear I didn’t mean to eat this much of the Void Linux thread on what appears to be a Blackbird-specific issue. If these posts could be moved elsewhere, I’d do it.
edit: a USB wireless networking dongle is working well enough for now… so I’m on a path forward, at least. Thanks.