I figured out why the Linux build was stalling (not emitting notifications) and not emitting events to the high speed event log. The two lines that emit the event and the notification were commented out in the current build, and I had been running the Windows builds one PR ahead of master. So nothing to do with Linux/Windows, same behavior.
I cancelled that larger PR and the fix is now merged here:
https://github.com/libbitcoin/libbitcoin-node/pull/689