Sometimes, things just don’t want to work as designed, you encounter Heisenbugs, random errors show up, and finding a rational explanation is way too much work. In these cases, “let things settle” is a perfectly valid strategy! L2CAP connection establishment was a bit flakey in Blunt, so I added a command to get the link quality before initiating the connection, delaying things a bit. Seems to work so far. And I got the first bytes sent over from the Newton as a connecting device to the Mac machine.
Starting a PPP daemon on the Mac to let the Newton establish a TCP/IP connection via Bluetooth should be possible now… but there is still lots of additional code required, especially the Internet Setup/Blunt coordination is missing (stuff like peer discovery, finding the correct RFCOMM port, handling pairing etc.)