I want to connect my Intel iMac to the Ubuntu machine. Can this be done, in theory, with 'Go > Connect to Server...' ?
(According to 'Connection Information' on the Ubu machine, it has an IP address 10.0.1.x, but attempted connections using this address have failed.)
The key here is that Ubuntu uses the same file sharing protocol (SMB/CIFS) as Windows boxes. Please check out the following Apple Support article for details. Also, be sure that you have configured your Ubuntu box for file sharing.