I think I can help with the LK201 as I have both the 8051 and 6805 variant PCBs here. I also have an EPROM programmer so I'll read the 8051 in at some point. However I've traced the wiring on the 6805 PCB and I pretty much know which pin goes where now. The keyboard matrix is the same for both variants. I've made a start on modifying dec_lk201.c and have got this at least partly working with the VT220. I've added the input ports for the keyboard matrix, the code to scan it, the code to drive the LEDs and some of the code for the SCI and SPI interfaces. I've tried joining it to the Rainbow but I'm having some difficulty working out how to (correctly) use device_serial_interface. Also the bytes being sent out via port 0x10 to the 8251 UART do not seem to be keyboard commands? Perhaps I did something wrong? I think between us we should be able to get this working.
I metioned the VT220, this is actually where I started. There are two variants of this: one with an 8051, two program ROMs and a character ROM and a later variant with an 8031 and a single program ROM. I have started implementing the earlier variant as that is the one for which documentation is available. It currenly passes about 20 of the (?) self tests, but the LK201 is going to be needed so I started looking at that.
I guess the next step will be to send some diffs to someone and hopefully they can help me with device_serial_interface and hooking this up to the rainbow to test it properly.