an SE/30 is pretty easy to get on the internet without extra hardware or Ethernet.

Install MacTCP and MacPPP on the SE/30

make a cross-over serial cable and connect it to a computer that you want to use as a ppp server.

configure the server to run a login screen with getty

configure the server to run the pppd server.

Then, you can set up a script in MacPPP to log in and initiate a ppp connection with the server. This will serve your TCP/IP connection through the serial port.

You will have a full internet conenction on the SE/30 without ethernet. This is how I get my Se/30 online.