Next step -- the color graphics board, KCGD. Text-only was easy since it uses 8080 and the ususal support chips, but KCGD (and its host system as well) uses an unique microprocessor implementation of pdp-11 ISA.
Some progress -- the board is talking to SIMH running Ultrix, and the shifted lines at the bottom are likely because of core bugs.
... and to find them I need to boot RT-11 and run tests from FTMON (XXDP workalike), but that is not easy -- in this screenshot RT-11 is running off virtual disk but not talking to the console for some reason: